Illuminated by knowledge? (11)
I believe the answer is:
enlightened
'illuminated' is the definition.
('enlighten' can be a synonym of 'illuminate')
'knowledge?' is the wordplay.
I cannot quite see how this works, but
'knowledge?' could be 'light' (light is a kind of knowledge) and 'light' is found in the answer.
This explanation may well be incorrect...
'by' is the link.
Can you help me to learn more?
(Other definitions for enlightened that I've seen before include "Rational, tolerant" , "Having spiritual insight" .)