Combusts (5)
I believe the answer is:
burns
'combusts' is the definition.
('burn' can be a synonym of 'combust')
This is the entire clue.
(Other definitions for burns that I've seen before include "feels strong emotion" , "experiences strong emotion" , "Scottish lyricist" , "Tam o' Shanter poet, d. 1796" , "Scots poet" .)