Having gin now shaken (6)
I believe the answer is:
owning
'having' is the definition.
('own' can be a synonym of 'have')
'gin now shaken' is the wordplay.
'shaken' is an anagram indicator.
'gin'+'now'='ginnow'
'ginnow' is an anagram of 'OWNING'.
(Other definitions for owning that I've seen before include "Being in possession or confessing" , "Possesing" , "Admitting" , "Conceding - possession" , "Possessing" .)