Get treatment, fit in (7)
I believe the answer is:
capture
'get' is the definition.
(synonyms)
'treatment fit in' is the wordplay.
'treatment' becomes 'cure' (cure is a kind of treatment).
'fit' becomes 'apt' (I've seen this before).
'in' indicates putting letters inside.
'cure' placed around 'apt' is 'CAPTURE'.
(Other definitions for capture that I've seen before include "Take prisoner" , "Ensnare" , "Take opponent's piece (chess)" , "Collar" , "Apprehend" .)