Clubs previously accepting present unity (9)
I believe the answer is:
coherence
'unity' is the definition.
(thesaurus)
'clubs previously accepting present' is the wordplay.
'clubs' becomes 'c' (abbreviation used in card games such as bridge).
'previously' becomes 'once' (I've seen this before).
'accepting' means one lot of letters goes inside another (inserted letters are accepted).
'present' becomes 'here' (both can mean in attendance).
'once' enclosing 'here' is 'oherence'.
'c'+'oherence'='COHERENCE'
(Other definitions for coherence that I've seen before include "Logical consistency" , "union" , "sense of unity" , "ability to talk sense" , "Sticking together" .)