Start being reformed (5)
I believe the answer is:
begin
'start' is the definition.
(I know that start can be written as begin)
'being reformed' is the wordplay.
'reformed' indicates anagramming the letters.
'being' anagrammed gives 'BEGIN'.
(Other definitions for begin that I've seen before include "Institute" , "Commence" , "Israeli prime minister who shared the Nobel Peace Prize with President Sadat" , "Israeli prime minister and Nobel Peace Prize winner, d. 1992" , "Found" .)