Men bowled over by fine bird … (4)
I believe the answer is:
rook
'bird' is the definition.
(rook is a kind of bird)
'men bowled over by fine' is the wordplay.
'men' becomes 'or' (military abbreviation for Other Ranks).
'bowled over' says the letters should be written in reverse.
'by' says to put letters next to each other.
'fine' becomes 'ok' (synonyms).
'or' backwards is 'ro'.
'ro'+'ok'='ROOK'
(Other definitions for rook that I've seen before include "Defraud -- crow" , "embattled man" , "Black bird - cheat - chess piece" , "16" , "Chesspiece otherwise known as a castle" .)