Victor loses his head going round the bull (5)
I believe the answer is:
inner
'going round the bull' is the definition.
I can't tell whether this defines the answer.
'victor loses his head' is the wordplay.
'victor' becomes 'winner' (synonyms).
'loses his head' means to remove the first letter.
'winner' with its first letter taken off is 'INNER'.
Can you help me to learn more?
(Other definitions for inner that I've seen before include "Area near to bull's-eye" , "Not a bad shot" , "Good shot at archery" , "(Of thoughts) intimate - (of circles) privileged" , "Opposite of outer" .)