It comes later to one in search of illumination (9)
I believe the answer is:
afterglow
'it comes later' is the definition.
The definition suggests a singular noun which matches the answer.
'one in search of illumination' is the wordplay.
'one in search' becomes 'after' (I've seen this in other clues).
'of illumination' becomes 'glow' (I am not sure about this - if you are sure you should believe this answer much more).
'after'+'glow'='AFTERGLOW'
'to' acts as a link.
Can you help me to learn more?
(Other definitions for afterglow that I've seen before include "Light once the actual source has gone" , "Pleasure of remembering something nice" , "trace of sunset" , "Remaining light" , "Light in the sky post sunset" .)