To start with, Benjamin embraces Joe (5)
I believe the answer is:
begin
'to start with' is the definition.
(I've seen this before)
'benjamin embraces joe' is the wordplay.
'benjamin' becomes 'ben' (short for Benjamin).
'embraces' means one lot of letters goes inside another.
'joe' becomes 'GI' (GI Joe).
'ben' enclosing 'gi' is 'BEGIN'.
(Other definitions for begin that I've seen before include "Monachem --" , "Institute" , "Make a start" , "Launch" , "Clandestine, furtive" .)