Prank not in support of clubs (5)
I believe the answer is:
antic
'prank' is the definition.
(synonyms)
'not in support of clubs' is the wordplay.
'not in support of' becomes 'anti' (I've seen this in another clue).
'clubs' becomes 'c' (abbreviation used in card games such as bridge).
'anti'+'c'='ANTIC'
(Other definitions for antic that I've seen before include "Caper; grotesque (arch.)" , "Tomfoolery" , "Absurd act" , "old buffoon" , "Playful caper" .)