Deviation gets through (3)
I believe the answer is:
via
'through' is the definition.
(via means going through)
'deviation gets' is the wordplay.
'gets' says the answer is hidden in the clue.
'VIA' is hidden in the letters of 'deviation'.
(Other definitions for via that I've seen before include "A Roman way" , "Passing through" , "Going through" , "By way of - in Latin" , "By means of" .)