He seeks to find out what the students know (8)
I believe the answer is:
examiner
'he seeks to find out what the students know' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'he' is the wordplay.
I cannot quite see how this works, but
'he' could be 'miner' and 'miner' is found in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for examiner that I've seen before include "Academic tester" , "One administering test" , "Who judges" , "One in charge of test" , "judge" .)