Man entering pub's rejected treatment (5)
I believe the answer is:
rehab
'treatment' is the definition.
(I have seen 'remedial treatment' mean 'rehab' so perhaps 'treatment' could also mean 'rehab')
'man entering pub's rejected' is the wordplay.
'man' becomes 'he'.
'entering' indicates putting letters inside.
'pub' becomes 'bar' (I've seen this before).
'rejected' is a reversal indicator.
'he' inserted into 'bar' is 'baher'.
'baher' reversed gives 'REHAB'.
(Other definitions for rehab that I've seen before include "A herb (anag.)" , "Training and therapy after drug abuse" , "Place to go, in short, to be restored to fitness" , "help with addiction" , "Process of restoring, eg, an addict to health" .)