Recovering, getting better (2,3,4)
I believe the answer is:
on the mend
I believe this is a double definition.
'recovering' is the first definition.
(I've seen this before)
'getting better' is the second definition.
(I've seen this before)
(Other definitions for on the mend that I've seen before include "Regaining health" , "Informally getting better, improving after illness or accident" , "undergoing recovery?" , "Improving in health" , "convalescing" .)