Mention as a reference (4)
I believe the answer is:
cite
'mention as a reference' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for cite that I've seen before include "Quote (eg, a book)" , "Quote as authority" , "Repeat a passage from some written work" , "Use quotations" , "Adduce as proof" .)