Mention dean fixed votes (9)
I believe the answer is:
referenda
'votes' is the definition.
(referendum is a kind of vote)
'mention dean fixed' is the wordplay.
'mention' becomes 'refer' (I can't justify this - if you can you should believe this answer much more).
'fixed' indicates anagramming the letters.
'dean' with letters rearranged gives 'enda'.
'refer'+'enda'='REFERENDA'
Can you help me to learn more?
(Other definitions for referenda that I've seen before include "decisions for people" , "National votes or plebiscites (9)" , "Votes put to country generally 9)" , "General votes" , "mass votes" .)