Seem unhappy to be a source of illumination? (6)
I believe the answer is:
glower
'a source of illumination?' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how they can define each other.
'seem unhappy' is the wordplay.
'seem' becomes 'glow' (glowing is a kind of seeming).
'unhappy' becomes 'er' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'glow'+'er'='GLOWER'
'to be' acts as a link.
Can you help me to learn more?
(Other definitions for glower that I've seen before include "Look black" , "firefly?" , "Glare" , "burning ember, say?" , "Frown" .)