Fancy woman seen with that bloke (4)
I believe the answer is:
whim
'fancy' is the definition.
(both can mean a notion or desire)
'woman seen with that bloke' is the wordplay.
'woman' becomes 'W' (abbreviation eg in Woman Police Constable).
'seen with' is a charade indicator (letters next to each other).
'that bloke' becomes 'him' (I've seen this in another clue).
'w'+'him'='WHIM'
(Other definitions for whim that I've seen before include "Fad" , "Sudden impulse" , "Urge" , "Sudden unusual change of mind" , "Caprice, sudden fancy" .)