Those people must accept rebuke for this treatment (7)
I believe the answer is:
therapy
'this treatment' is the definition.
(synonyms)
'those people must accept rebuke' is the wordplay.
'those people' becomes 'they' (I've seen this before).
'must accept' is an insertion indicator.
'rebuke' becomes 'rap' (rap is a kind of rebuke).
'they' going around 'rap' is 'THERAPY'.
'for' is the link.
(Other definitions for therapy that I've seen before include "Treatment designed to cure illness or disability" , "Healing treatment" , "Medical treatment" , "See 7" , "will do you good" .)