Burn unsteadily (7)
I believe the answer is:
flicker
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">burn unsteadily</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for flicker that I've seen before include "Twinkle" , "Shine unsteadily; waver" , "Vary rapidly in brightness" , "Burn or shine unsteadily" , "Woodpecker" .)