Author can't serve bananas (9)
I believe the answer is:
cervantes
'author' is the definition.
(I've seen this before)
'can't serve bananas' is the wordplay.
'bananas' is an anagram indicator (informal term for mad).
'cant'+'serve'='cantserve'
'cantserve' is an anagram of 'CERVANTES'.
(Other definitions for cervantes that I've seen before include "Spanish writer" , "Bookmaker" , "Author of the novel 'Don Quixote'" .)