Some candles are so incandescent (8)
I believe the answer is:
incensed
I believe this is a double definition.
'some candles are so' is the first definition.
(some candles have incense)
'incandescent' is the second definition.
(both can mean very angry)
(Other definitions for incensed that I've seen before include "Cross" , "Very angry, really mad" , "Enraged, furious" , "A high church may become so" , "Livid" .)