Welcome guys inside following a deal (9)
I believe the answer is:
agreement
'deal' is the definition.
(I know that deal can be written as agreement)
'welcome guys inside following a' is the wordplay.
'welcome' becomes 'greet' (I've seen this before).
'guys' becomes 'men' (guy can mean a man).
'inside' is an insertion indicator.
'following' is a charade indicator (letters next to each other).
'greet' enclosing 'men' is 'greement'.
'greement' put after 'a' is 'AGREEMENT'.
(Other definitions for agreement that I've seen before include "concert" , "legal contract maybe" , "consensus" , "State of being consistent" , "deal" .)