Working with those people with aim to be getting better (2,3,4)
I believe the answer is:
on the mend
Here is my best explanation:
'be getting better' is the definition.
(I've seen this before)
'working with those people with aim' is the wordplay.
'working' becomes 'on'.
'with' means one lot of letters go next to another.
'those people' becomes 'them' (I've seen this before).
'with' is a charade indicator (letters next to each other).
'aim' becomes 'end' (I've seen this before).
'on'+'them'+'end'='ON THE MEND'
'to' acts as a link.