Those people taking hit for rehab treatment (7)
I believe the answer is:
therapy
'rehab treatment' is the definition.
(I've seen this in another clue)
'those people taking hit' is the wordplay.
'those people' becomes 'they' ('they' refers to a group of people).
'taking' means one lot of letters goes inside another.
'hit' becomes 'rap' (rap can mean to knock or hit).
'they' going around 'rap' is 'THERAPY'.
'for' acts as a link.
(Other definitions for therapy that I've seen before include "Remedial treatment" , "Curative treatment" , "healing process" , "will do you good" , "Medical treatment" .)