That fellow in pub backed treatment for alcoholism? (5)
I believe the answer is:
rehab
'treatment for alcoholism?' is the definition.
(where alcoholics might be treated)
'that fellow in pub backed' is the wordplay.
'that fellow' becomes 'he' ('he' refers to a man).
'in' indicates putting letters inside.
'pub' becomes 'bar' (both are drinking establishments).
'backed' shows that the letters should be reversed in order.
'he' placed inside 'bar' is 'baher'.
'baher' in reverse letter order is 'REHAB'.
(Other definitions for rehab that I've seen before include "help with addiction" , "Alcohol clinic" , "convalescent home?" , "Treatment for addicts (abbrev.)" , "Rehabilitation (abbrev.)" .)