Getting better outcome following their treat (2,3,4)
I believe the answer is:
on the mend
'getting better' is the definition.
(on the mend means recovering from illness)
'outcome following their treat' is the wordplay.
I cannot quite understand how this works, but
'outcome' could be 'end' (I've seen this in other clues) and 'end' is present in 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 on the mend that I've seen before include "Making recovery" , "Recovering from an injury or illness" , "Regaining health" , "Improving in health" , "Looking up" .)