Perfectionist's fine American pickle (7)
I believe the answer is:
'perfectionist's' is the definition.
(thesaurus)
'fine american pickle' is the wordplay.
'fine' becomes 'f' (abbreviation).
'american' becomes 'us'.
'pickle' becomes 'spot' (I've seen this before).
'f'+'us'+'spot'='FUSSPOT'
(Other definitions for fusspot that I've seen before include "I worry" , "song-and-dance man?" , "Over-fastidious person" , "One who worries too much" , "Finicky person" .)