Become established (3,2)
'become established' is the definition.
(synonyms)
This is the entire clue.
(Another definition for set in that I've seen is " Become established".)
'become established' is the definition.
(synonyms)
This is all the clue.
(Other definitions for take root that I've seen before include "Send down shoots or become established" , "Settle down" , "Embed firmly" , "perform mathematical task" .)