Big buzzer in trumpet film (6)
I believe the answer is:
hornet
'big buzzer' is the definition.
(I've seen this in another clue)
'trumpet film' is the wordplay.
'trumpet' becomes 'horn' (synonyms).
'film' becomes 'ET' (E.T. the Extra-Terrestrial).
'horn'+'et'='HORNET'
'in' is the link.
(Other definitions for hornet that I've seen before include "Run through" , "Large social wasp with fierce sting" , "Large stinging wasp" , "Stingy type" , "Small flier" .)