Pretty fine tune (4)
I believe the answer is:
fair
'pretty' is the definition.
(thesaurus)
'fine tune' is the wordplay.
'fine' becomes 'f' (abbreviation).
'tune' becomes 'air' (I've seen this before).
'f'+'air'='FAIR'
(Other definitions for fair that I've seen before include "Favourable" , "Women are known as the ... sex" , "Market for the sale of produce" , "clear" , "Pretty; impartial" .)