Victor taking whiskey in secret (5)
I believe the answer is:
inner
'secret' is the definition.
(thesaurus)
'victor taking whiskey' is the wordplay.
'victor' becomes 'winner' ('winner' can be a synonym of 'victor').
'taking' is a deletion indicator.
'whiskey' becomes 'w' (alpha bravo charlie delta ...).
'winner' with 'w' taken away is 'INNER'.
'in' acts as a link.
(Other definitions for inner that I've seen before include "(Of thoughts) intimate - (of circles) privileged" , "Located inward" , "Ring round the target bull." , "It's next to the bull on the board" , "This part of city is at the old centre" .)