He may be able to sail (6)
I believe the answer is:
seaman
'he may be able to sail' 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 'man' (I've seen this in another clue) and 'man' is found within the answer.
The remaining letters 'sea' 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 seaman that I've seen before include "Mariner" , "crew member" , "A manse (anag.)" , "Sailor" .)