Victor losing head in ring (5)
I believe the answer is:
inner
'ring' is the definition.
(I've seen this before)
'victor losing head' is the wordplay.
'victor' becomes 'winner' ('winner' can be a synonym of 'victor').
'losing head' means to remove the first letter.
'winner' with its initial letter taken off is 'INNER'.
'in' is the link.
(Other definitions for inner that I've seen before include "closer than magpie" , "Situated within" , "Target next to the bull's-eye on a dart board" , "Private, not expressed" , "Located inside" .)