A killer in the ring (7)
I believe the answer is:
matador
'a killer' is the definition.
(I've seen this before)
'the ring' is the wordplay.
I cannot really see how this works, but
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is located in the answer.
'ring' could be 'o' (letter resembling a ring) and 'o' is found within the answer.
This may be the basis of the clue (or it may be nonsense).
'in' is the link.
Can you help me to learn more?
(Other definitions for matador that I've seen before include "A bull-fighter.11 Beginning to develop" , "He kills the bull in formal fight" , "Bullfighter who slays the bull" , "The one who kills the bull" , "he aims to get a bull" .)