Define a macro that eliminates this repetitive pattern:
(make-instance* 'class :c c :b b (when something (list :a a)))

Issue: Macro call that should be transformed by make-instance*

Macro definition:
(defmacro make-instance* (class &rest arguments)
  "Convenience macro on top of `make-instance'.

Conveniences:

- First argument can be a (possibly empty) list of shortcut symbols,
  which is automatically converted into a KEYWORD+SYMBOL pairs where
  - KEYWORD is the same as shortcut name, but interned as keyword.
  - And SYMBOL is the same as shortcut.

- The last argument can be an apply argument---arbitrary
  list-producing form, which will be used as the last argument
  to (apply #'make-instance ...) idiom.

Note that using a singular shortcut list of apply argument is an
ambiguous case that will be interpreted in favor of apply argument. To
force either of interpretations, provide shortcuts and apply arguments
explicitly:
(make-instance* 'class (a b c)) ;; BAD
(make-instance* 'class (a b c) nil) ;; GOOD
(make-instance* 'class (when t nil)) ;; BAD
(make-instance* 'class () (when t nil)) ;; GOOD

Otherwise, the behavior is equivalent to `make-instance'.

Examples:

Shortcut args:
\(make-instance* 'class (a b c))
=>
\(make-instance 'class :a a :b b :c c)

Last form converted into `apply' argument:
\(make-instance* 'class :c c :b b (when something (list :a a)))
=>
\(apply #'make-instance 'class :c c :b b (when something (list :a a)))

Shortcut arguments, regular arguments, and form for `apply':
\(make-instance* 'class (b c) :x x (when something (list :a a)))
=>
\(apply #'make-instance 'class :b b :c c :x x (when something (list :a a)))

Form for `apply' (notice the empty shortcuts---these are required for
unambiguous parsing):
\(make-instance* 'class () (when something (list :a a)))
=>
\(apply #'make-instance 'class (when something (list :a a)))

Regular `make-instance'-like use:
\(make-instance* 'class :a a-value :b b-value)
=>
\(make-instance 'class :a a-value :b b-value)"
  (when (and (= 1 (length arguments))
             (listp (first arguments)))
    (style-warn "Body of MAKE-INSTANCE* contains a single list-like form ~a.

If you meant APPLY args, add empty shortcuts list:
(make-instance* 'class () (apply-form))

If you meant shortcut list, add empty APPLY args:
(make-instance* 'class (shortcuts) nil)

Interpreting as APPLY args for now, but this behavior may change in
the future." arguments))
  (let* ((shortcuts-p (and (listp (first arguments))
                           (> (length arguments) 1)))
         (shortcuts (when shortcuts-p
                      (first arguments)))
         (arguments (if shortcuts-p
                        (rest arguments)
                        arguments))
         (last-appendable-form-p (oddp (length arguments)))
         (last-appendable-form (when last-appendable-form-p
                                 (first (last arguments))))
         (arguments (if last-appendable-form-p
                        (butlast arguments)
                        arguments)))
    `(,@(if last-appendable-form-p
            `(apply #'make-instance)
            `(make-instance))
      ,class
      ,@(loop for shortcut in shortcuts
              append (list (intern (symbol-name shortcut) :keyword)
                           shortcut))
      ,@arguments
      ,@(when last-appendable-form-p
          (list last-appendable-form)))))

Macroexpansion:
(apply (function make-instance) (quote class) :c c :b b (when something (list :a a)))