Choose snippet of film dialogue for demo (6,4)
I believe the answer is:
picket line
'demo' is the definition.
'choose snippet of film dialogue' is the wordplay.
I cannot really understand how this works, but
'choose' could be 'pick' (picking is a kind of choosing) and 'pick' is located in the answer.
'film' could be 'et' and 'et' is located in the answer.
The remaining letters 'line' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
'for' acts as a link.
(Other definitions for picket line that I've seen before include "Strike enforcers" , "Striking protest" , "Barrier established by strikers" , "Some in labour dispute" .)