Sit on the throne with it close to backside, and burn again (8)
I believe the answer is:
reignite
'burn again' is the definition.
('ignite' is an answer for 'burn' so perhaps 'reignite' is OK for 'burn again')
'sit on the throne with it close to backside' is the wordplay.
'sit on the throne' becomes 'reign' (reign as a monarch).
'with' means one lot of letters go next to another.
'close to' says to take the final letters (the close/ending of).
The last letter of 'backside' is 'e'.
'reign'+'it'+'e'='REIGNITE'
'and' acts as a link.
(Other definitions for reignite that I've seen before include "Set fire to - again" , "What one may do to old controversy" , "torch again" , "Once again, send up" , "Light again" .)