Centrists in Boston, unable to stick the knife in (4)
I believe the answer is:
stab
'knife in' is the definition.
'stab' can be an answer for 'knife' (synonyms). I'm unsure of the 'in' bit.
'centrists in boston unable to stick the' is the wordplay.
I cannot quite see how this works, but
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is found in the answer.
The remaining letters 'sab' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for stab that I've seen before include "Sudden sharp feeling" , "Injure with knife" , "pink" , "Wound with a dagger" , "Go" .)