Order fellows into risky venture (6)
I believe the answer is:
behest
'order' is the definition.
(thesaurus)
'fellows into risky venture' is the wordplay.
'fellows' becomes 'hes' ('he' can refer to a fellow).
'into' means one lot of letters goes inside another.
'risky venture' becomes 'bet'.
'hes' inserted within 'bet' is 'BEHEST'.
(Other definitions for behest that I've seen before include "Command - Thebes (anag)" , "Order" , "(At someone's) command" , "Command, bidding" .)