Could nothing spoil him? (4)
I believe the answer is:
omar
'him?' is the definition.
'could nothing spoil' is the wordplay.
I cannot really understand how this works, but
'nothing' could be 'o' (looks like zero - 0) and 'o' is found within the answer.
'spoil' could be 'mar' (synonyms) and 'mar' is present in the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for omar that I've seen before include "- Khayyam, Pers. poet" , "- Khayyam, Persian poet, astronomer and mathematician" , "and 16 Down: Persian poet" , "Old caliph" , "old poet" .)