Game OK, Celtic having brought in a winger (9)
I believe the answer is:
cockatiel
'winger' is the definition.
(cockatiel is a kind of bird)
'game ok celtic having brought in a' is the wordplay.
'game' is an anagram indicator (solving anagrams is a game).
'having brought in' indicates putting letters inside.
'ok'+'celtic'='okceltic'
'okceltic' with letters rearranged gives 'cocktiel'.
'cocktiel' going around 'a' is 'COCKATIEL'.
(Other definitions for cockatiel that I've seen before include "18's [BIRD]" , "Small crested Australian parrot" .)