Clue: Dog left to bite bespectacled nebbish, one nowadays missing a lead? (6,4)
Answer: FALLEN IDOL
Explanation: Definition: one nowadays missing a lead?
=someone who has lost their position as a leader/role model
 **FIDO**="Dog" + **L**(eft); around **ALLEN**="bespectacled nebbish"
 'nebbish' is a term often applied to Woody Allen, and means 'someone with a timid personality'