Seemed angered by, which was all too illuminating (6)
I believe the answer is:
glared
This might be a double definition.
'seemed' is the first definition.
The answer and definition can be both to do with perception as well as being past participle verbs.
Perhaps you can see an association between them that I don't see?
'angered by which was all too illuminating' is the second definition.
Although both the answer and definition are past participle verbs, I don't understand how they can define each other.
Can you help me to learn more?
(Other definitions for glared that I've seen before include "Was too bright" , "Glowered" , "Lowered" , "Stared fiercely" , "Looked angrily" .)