Start, commence (5)
I believe the answer is:
begin
I believe this clue is a double definition.
'start' is the first definition.
(I know that start is a kind of begin)
'commence' is the second definition.
(I know that commence is a kind of begin)
(Other definitions for begin that I've seen before include "Institute" , "Make a start" , "former Israeli Nobel peace prize winner" , "Launch" , "Monachem --" .)