Men come in to say hello following a consensus (9)
I believe the answer is:
agreement
'consensus' is the definition.
(I've seen this before)
'men come in to say hello following a' is the wordplay.
'come in' indicates putting letters inside.
'to say hello' becomes 'greet' (I've seen this in another clue).
'following' is a charade indicator (letters next to each other).
'men' put into 'greet' is 'greement'.
'greement' put after 'a' is 'AGREEMENT'.
(Other definitions for agreement that I've seen before include "Contract or promise" , "in sympathy" , "Union < matching" , "concert" , "Harmony or treaty" .)