Soon to feel unhappy about engaging in work (9)
I believe the answer is:
presently
'soon' is the definition.
(I know that soon can be written as presently)
'engaging in work' is the wordplay.
'engaging' becomes 'resent' (I am not sure about this - if you are sure you should believe this answer much more).
'in' is an insertion indicator.
'work' becomes 'ply' (to ply a trade is to work at it).
'resent' put within 'ply' is 'PRESENTLY'.
'to feel unhappy about' is the link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for presently that I've seen before include "Soon, in a little while" , "At the moment" , "Before long" , "In the near future" .)