Fully briefed, as one chosen by casting director may be? (2,3,7)
I believe the answer is:
in the picture
'fully briefed' is the definition.
(in the picture means given information)
'one chosen by casting director may be?' is the wordplay.
I cannot really see how this works, but
'one' could be 'the' (both can introduce a definite example of something) and 'the' is present in the answer.
'chosen' could be 'in' ('you're in!') and 'in' is found in the answer.
The remaining letters 'picture' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
'as' is the link.
Can you help me to learn more?
(Other definitions for in the picture that I've seen before include "where star may be seen?" , "stars' location" , "what the subject of a portrait must be" , "Genned up" , "where stars may be seen?" .)