Was monarch set on fire again after losing it? (7)

I believe the answer is:
reigned
'was monarch' is the definition.
(I've seen this before)
'on fire again after losing it?' is the wordplay.
I cannot quite understand how this works, but
'on' could be 're' (regarding) and 're' is found within the answer.
'it?' could be 'e' ('e' can mean 'electronic' which is similar to 'IT') and 'e' is found in the answer.
This explanation may well be incorrect...
'set' is the link.
Can you help me to learn more?
(Other definitions for reigned that I've seen before include "Was monarch" , "Had sovereign power" , "Was king" , "Ruled" , "Held sway" .)
