Turn aside soldier back in uniform (7)
I believe the answer is:
digress
'turn aside' is the definition.
(thesaurus)
'soldier back in uniform' is the wordplay.
'soldier' becomes 'GI' (GI can mean a US soldier).
'back' shows that the letters should be reversed in order.
'in' means one lot of letters goes inside another.
'uniform' becomes 'dress' (dress uniform is a kind of uniform).
'gi' backwards is 'ig'.
'ig' put into 'dress' is 'DIGRESS'.
(Other definitions for digress that I've seen before include "Go off the main subject" , "Deviate from the main subject" , "Wander from a topic" , "Ramble" , "Leave the main subject" .)