He'll hand out a sub, perhaps (7)
I believe the answer is:
husband
'he'll' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'hand out a sub perhaps' is the wordplay.
'out' is an insertion indicator.
'perhaps' indicates anagramming the letters.
'sub' is an anagram of 'usb'.
'hand' placed around 'usb' is 'HUSBAND'.
Can you help me to learn more?
(Other definitions for husband that I've seen before include "Farm" , "Groom" , "Married man" , "Economically manage" , "Use resources economically" .)