The man put in foremost command (6)
I believe the answer is:
behest
'command' is the definition.
(I know that behest is a type of command)
'the man put in foremost' is the wordplay.
'the man' becomes 'he' (he refers to a man).
'put in' indicates putting letters inside.
'foremost' becomes 'best' (similar in meaning).
'he' placed into 'best' is 'BEHEST'.
(Other definitions for behest that I've seen before include "Order" , "Command, bidding" , "(At someone's) command" , "Command - Thebes (anag)" .)