He's still not able in the main (8,6)
I believe the answer is:
ordinary seaman
'he's still not able in the main' is the definition.
The definition suggests a singular noun which matches the answer.
'he's still not able in the main' is the wordplay.
I cannot really see how this works, but
'not' could be 'nary' (I've seen this in another clue) and 'nary' is found within the answer.
'main' could be 'sea' (the main is an old name for the sea) and 'sea' is located in the answer.
'he' could be 'man' (I've seen this in another clue) and 'man' is found within the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for ordinary seaman that I've seen before include "Lowest rank of Royal Navy sailor" , "Crew member" , "OS in full" .)