Understand instinctively (6)
I believe the answer is:
intuit
'understand instinctively' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for intuit that I've seen before include "work things out instinctively" , "Feel" , "Work out by instinct" , "Understand instinctively" , "Perform (role) in exaggerated manner" .)