Punishment constrains everyone in revolutionary group to conform (4,4,4)
I believe the answer is:
fall into line
'conform' is the definition.
(I've seen this before)
'punishment constrains everyone in revolutionary group' is the wordplay.
'punishment' becomes 'fine' (fine is a kind of punishment).
'constrains' indicates putting letters inside.
'everyone' becomes 'all' (I've seen this before).
'in revolutionary group' becomes 'intol' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'all'+'intol'='allintol'
'fine' enclosing 'allintol' is 'FALL INTO LINE'.
'to' acts as a link.
(Other definitions for fall into line that I've seen before include "Conform with accepted behaviour" , "be conventional" , "Dutifully conform" .)