Start being clever (5)
I believe the answer is:
begin
'start' is the definition.
('begin' can be a synonym of 'start')
'being clever' is the wordplay.
'clever' indicates an anagram.
'being' with letters rearranged gives 'BEGIN'.
(Other definitions for begin that I've seen before include "Israeli prime minister and Nobel Peace Prize winner, d. 1992" , "Commence" , "Partly open" , "Institute" , "Israeli statesman" .)