Smouldering anger? (7)
I believe the answer is:
incense
'anger?' is the definition.
(to incense is make angry)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for incense that I've seen before include "Perfume - inflame with anger" , "Exasperate" , "Enrage; fragrant resin" , "Make very angry about the fragrant smoke?" , "Provoke" .)