### Clue: Boiler fixed by unknown bloke once offering staff work? (7)
### Answer: BERLIOZ 
 ### Explanation: Definition: bloke once offering staff work
 **Anagram of**(… fixed) BOILER **plus**(by) Z(symbol for an unknown quantity in maths).
Defn: A chap/bloke who once composed artistic work/music with notes written in staffs/staves/the sets of parallel lines.
Answer: .., Hector, French Romantic composer.