...away when not well (3)
I believe the answer is:
off
'away' is the definition.
(synonyms)
'not well' is the wordplay.
'not' becomes 'o' (I've seen this in other clues).
'well' becomes 'ff' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'o'+'ff'='OFF'
'when' is the link.
Can you help me to learn more?
(Other definitions for off that I've seen before include "Of food, begining to decay" , "below par" , "(Of food) no longer fresh" , "away from the kerb" , "Away, or no longer on the menu perhaps" .)