Treatment facility in pub holding male back (5)
I believe the answer is:
rehab
'treatment facility' is the definition.
(facility for treating addiction)
'pub holding male back' is the wordplay.
'pub' becomes 'bar' (I've seen this before).
'holding' means one lot of letters goes inside another.
'male' becomes 'he'.
'back' is a reversal indicator.
'bar' placed around 'he' is 'baher'.
'baher' back-to-front is 'REHAB'.
'in' acts as a link.
(Other definitions for rehab that I've seen before include "remedial treatment" , "Treatment for addicts (abbrev.)" , "Alcohol clinic" , "brief convalescence?" , "A herb (anag.)" .)