Instigate
There are a few possibilities for this:
foment
'instigate' is the definition.
(thesaurus)
This is the entire clue.
(Other definitions for set on that I've seen before include "Attack" , "Determined" , "Go" .)
'instigate' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for foment that I've seen before include "Instigate, stir up" , "Arouse or stimulate, perhaps trouble" , "Arouse or stimulate, maybe trouble" , "Stir up, cause trouble" , "Stir up or stimulate, say trouble" .)