Bloomers in game against Premier League side (9)
I believe the answer is:
larkspurs
'bloomers' is the definition.
(type of flowering plant)
'game against premier league side' is the wordplay.
'game' becomes 'lark' (both can mean a bit of fun).
'against' says to put letters next to each other.
'premier league side' becomes 'Spurs' (Tottenham Hotspurs FC).
'lark'+'spurs'='LARKSPURS'
'in' is the link.
(Other definitions for larkspurs that I've seen before include "bloomers" , "Common names for delphiniums" .)