It's a hand he wants (6)
I believe the answer is:
suitor
'he wants' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'it's a hand' is the wordplay.
I cannot quite see how this works, but
'hand' could be 'r' (abbreviation for right, as in the right-hand side) and 'r' is present in the answer.
'it' could be 't' (abbreviation. e.g. in 'tis) and 't' is found in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for suitor that I've seen before include "Prospective husband" , "Man who courts a woman" , ". . . he woos his girl" , "One seeking marriage" , "It's our (anag) - admirer" .)