Though not much good, he has been capped (5)
I believe the answer is:
dunce
'though not much good he has been capped' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'he has been capped' is the wordplay.
I cannot quite understand how this works, but
'he' could be 'dunc' and 'dunc' is located in the answer.
A single letter 'e' remains which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for dunce that I've seen before include "Stupid man!" , "Bad scholar, may wear a paper cap" , "Dullard" , "Blockhead" , "Dull chap" .)