Subpoena in which great many mentioned (4)
I believe the answer is:
cite
'subpoena' is the definition.
(thesaurus)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for cite that I've seen before include "Adduce as proof" , "Repeat a passage from some written work" , "Summons - quote" , "Quote as an example or in support" , "Quote (eg, a book)" .)