Propose Mina in a brief message (8)
I believe the answer is:
nominate
'propose' is the definition.
(nominating is a kind of proposing)
'mina in a brief message' is the wordplay.
'in' indicates putting letters inside.
'a brief message' becomes 'note' (I've seen this in another clue).
'mina' inserted into 'note' is 'NOMINATE'.
(Other definitions for nominate that I've seen before include "Propose - a mention (anag)" , "Put forward name for a mention" , "Specify (person for job)" , "Propose - name" , "Pick as a candidate" .)