He'll admit he's got something (5)
I believe the answer is:
owner
'he's got something' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'he'll admit' is the wordplay.
I cannot really understand how this works, but
'admit' could be 'own' (own can mean to admit or acknowledge) and 'own' is located in the answer.
The remaining letters 'er' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for owner that I've seen before include "The person in legal possession" , "landlord" , "One who has something" , "possessive type" , "The person in lawful possession" .)