Get off on fire (6)
I believe the answer is:
alight
This clue is a double definition.
'get off' is the first definition.
(I've seen this before)
'on fire' is the second definition.
(synonyms)
(Other definitions for alight that I've seen before include "Land; on fire" , "Land, come down" , "Brilliant" , "Get off the bus because it's on fire" , "Settle; on fire" .)