Start, say, filling waste container (5)
I believe the answer is:
begin
'start' is the definition.
(I know that start can be written as begin)
'say filling waste container' is the wordplay.
'say' becomes 'eg' (both can mean for example).
'filling' indicates putting letters inside.
'waste container' becomes 'bin' (rubbish bin).
'eg' placed into 'bin' is 'BEGIN'.
(Other definitions for begin that I've seen before include "Israeli statesman" , "Israeli prime minister and Nobel Peace Prize winner, d. 1992" , "Israeli prime minister who shared the Nobel Peace Prize with President Sadat" , "Commence" , "Institute" .)