Cotton on? (3)
(Other definitions for see that I've seen before include "Witness; ensure" , "Diocese of a bishop" , "Bishops office" , "Observe the bishop's jurisdiction" , "Glimpse; get" .)
'cotton on' is the definition.
(both can mean to realise something)
This is the entire clue.
(Other definitions for twig that I've seen before include "Latch on" , "Only a minor branch" , "Finally understand" , "Small piece of tree" , "Small part of tree - suddenly understand" .)