Arthur, when he won Wimbledon (4)
I believe the answer is:
ashe
'won wimbledon' is the definition.
The definition suggests a singular noun which matches the answer.
'arthur when he' is the wordplay.
I cannot really see how this works, but
'when' could be 'as' (eg 'when I walked' means 'as I walked') and 'as' is found within the answer.
'he' is within the answer.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for ashe that I've seen before include "Arthur, first black Wimbledon men's singles champion, 1975" , "Sporting champion once" , "Arthur ___, American tennis player 1943-1993" , "Ex-Wimbledon champ" , "US tennis player Arthur, 1975 Wimbledon champion" .)