Undergoes combustion (5)
I believe the answer is:
burns
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">undergoes combustion</span>' is the definition.<br/ ><span class="explanation-format__explanation">('burn' can be a synonym of 'undergo combustion')</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for burns that I've seen before include "Is on fire" , "experiences strong emotion" , "Cremates -- Scottish poet, d.1796" , "Scottish lyricist" , "Rabbie - - (poet)" .)