Mention may be made of it at the interview (9)
I believe the answer is:
'mention' is the definition.
(I know that mention can be written as reference)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for reference that I've seen before include "Book in which to find authoritative facts" , "Allusion - character report" , "Recommendation by a former employer" , "Allusion, mention" , "Formal recommendation to an employer" .)