Banishment (5)
(Other definitions for sidle that I've seen before include "Isled (anag.)" , "Walk sideways in furtive manner" , "Walk stealthily" , "Walk obliquely" , "Slink, creep, sneak" .)
'banishment' is the definition.
(exile is a kind of banishment)
This is all the clue.
(Other definitions for exile that I've seen before include "Ostracism" , "Banish from one's country" , "Car journey" , "being always away from home" , "Banish; expel" .)