He may have to wait for his money (7)
I believe the answer is:
servant
'have to wait for his money' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'he' is the wordplay.
I cannot really see how this works, but
'he' could be 'van' and 'van' is present in the answer.
The remaining letters 'sert' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
'may' is the link.
Can you help me to learn more?
(Other definitions for servant that I've seen before include "One working for another" , "Personal attendant" , "Worker in household" , "Domestic, lackey" , "Helper or attendant (sometimes humble or obedient?)" .)