Against clubs playing? (3)
I believe the answer is:
con
'against' is the definition.
(thesaurus)
'clubs playing?' is the wordplay.
'clubs' becomes 'c' (abbreviation used in card games such as bridge).
'playing?' becomes 'on'.
'c'+'on'='CON'
(Other definitions for con that I've seen before include "Not supporting" , "Swindle, deception" , "Have a reason not to" , "Dupe" , "Study - swindle" .)