Beginning working as a film actor (5)
I believe the answer is:
onset
'beginning' is the definition.
(I know that beginning can be written as onset)
'working as a film actor' is the wordplay.
I cannot quite see how this works, but
'working' could be 'on' (on can mean working or activated) and 'on' is present in the answer.
'film' could be 'et' (E.T. the Extra-Terrestrial) and 'et' is located in the answer.
A single letter 's' remains which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for onset that I've seen before include "Start - opening moments" , "Assault; beginning" , "Appearance of" , "Kick-off" , "Start - notes (anag)" .)