Editing letters that may be set on fire (7)
I believe the answer is:
ignited
'set on fire' is the definition.
(I've seen this before)
'editing letters' is the wordplay.
'letters' indicates an anagram.
'editing' with letters rearranged gives 'IGNITED'.
'that may be' is the link.
(Other definitions for ignited that I've seen before include "Set on fire" , "Sparked off" , "fired" , "Lit" , "Kindled" .)