After working, other people stop improving (2,3,4)
I believe the answer is:
on the mend
'improving' is the definition.
(on the mend means improving after an illness)
'after working other people stop' is the wordplay.
'after' is a charade indicator (letters next to each other).
'working' becomes 'on' (on can mean working or activated).
'other people' becomes 'them' (those people over there).
'stop' becomes 'end' (synonyms).
'on'+'them' is 'onthem'.
'onthem'+'end'='ON THE MEND'
(Other definitions for on the mend that I've seen before include "Regaining health" , "Informally getting better, improving after illness or accident" , "convalescing" , "Making recovery" , "Recovering from an injury or illness" .)