Victor spilling wife's secret (5)
I believe the answer is:
inner
'secret' is the definition.
(as in one's inner thoughts)
'victor spilling wife's' is the wordplay.
'victor' becomes 'winner' (synonyms).
'spilling' indicates named letters should be taken away (deleted letters spill out).
'wife' becomes 'w' (abbreviation).
'winner' with 'w' taken away is 'INNER'.
(Other definitions for inner that I've seen before include "Bull's penned in by this" , "Part of an archery target" , "red" , "Part of the bull" , "Not quite bull's-eye" .)