Long trousers affected Ashe's game (8)
I believe the answer is:
pheasant
'game' is the definition.
'long trousers affected ashe's' is the wordplay.
'long' becomes 'pant' (I've seen this in other clues).
'trousers' means one lot of letters goes inside another (trouser can mean to steal or take).
'affected' indicates an anagram.
'ashe' anagrammed gives 'heas'.
'pant' enclosing 'heas' is 'PHEASANT'.
(Other definitions for pheasant that I've seen before include "something to pluck?" , "Colourful game bird" , "Cock" , "Ant heaps (anag.)" , "Game-bird" .)