He gets what's left (7)
I believe the answer is:
legatee
'he gets' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'left' is the wordplay.
I cannot really understand how this works, but
'left' could be 'leg' (left leg) and 'leg' is present in the answer.
The remaining letters 'atee' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
'what's' is the link.
Can you help me to learn more?
(Other definitions for legatee that I've seen before include "Beneficiary of a will" , "One receiving a bequest" , "One receiving something left in a will" , "Receiver of money from a will" , "Person receiving a bequest" .)