Left in revolt change course (7)
I believe the answer is:
deflect
'change course' is the definition.
(I've seen this before)
'left in revolt' is the wordplay.
'left' becomes 'L' (common abbreviation).
'in' is an insertion indicator.
'revolt' becomes 'defect' (defect can mean to rebel).
'l' inserted within 'defect' is 'DEFLECT'.
(Other definitions for deflect that I've seen before include "Swerve" , "Parry, turn aside" , "Cause to go off course" , "Turn aside from an intended course" , "Turn from straight course" .)