Soon rule clubs out (4)
I believe the answer is:
anon
'soon' is the definition.
(synonyms)
'rule clubs out' is the wordplay.
'rule' becomes 'canon' (canon can mean a law).
'clubs' becomes 'c' (abbreviation used in card games such as bridge).
'out' suggests deleting specific letters.
'canon' with 'c' taken out is 'ANON'.
(Other definitions for anon that I've seen before include "Not identified by name" , "Of unknown authorship" , "In due course" , "Soon, shortly (archaic)" , "Soon, precious stone" .)