Hear about British drug treatment (5)
I believe the answer is:
rehab
'treatment' is the definition.
(eg treatment for a drug addict)
'hear about british drug' is the wordplay.
'about' says to put letters next to each other.
'british' becomes 'b' (abbreviation e.g. in BBC).
'drug' indicates anagramming the letters (I've seen 'drugged' mean this).
'hear' put after 'b' is 'bhear'.
'bhear' with letters rearranged gives 'REHAB'.
(Other definitions for rehab that I've seen before include "brief convalescence?" , "Rehabilitation (abbrev.)" , "Course of treatment for addicts" , "remedial treatment" , "Restorative care" .)