Pieces father wins? Not one! (5)
I believe the answer is:
pawns
'pieces' is the definition.
(pawn is a kind of piece)
'father wins? not one' is the wordplay.
'father' becomes 'pa' (pa can mean dad or father).
'not' indicates named letters should be taken away.
'one' becomes 'i' (Roman numeral).
'wins' with 'i' taken away is 'wns'.
'pa'+'wns'='PAWNS'
(Other definitions for pawns that I've seen before include "made pledges" , "Chess pieces" , "The foot-soldiers in chess" , "Minor chessmen" , "Men on board" .)