He's not unemployed, but he never does a day's work
I believe the answer is:
nightwatchman
'work' is the definition.
(I know this)
'he's not unemployed but he never does a day's' is the wordplay.
I cannot quite understand how this works, but
'he' could be 'wat' and 'wat' is found in the answer.
'a' could be 'an' and 'an' is located in the answer.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for nightwatchman that I've seen before include "one who may take guard close to stumps?" , "Someone promoted up the ordinary batting order when a wicket falls close to the end of the day's play" , "Inferior batsman" , "Poorer batsman sent in early, towards the end of play" , "Guard of premises not in use" .)