Film dog eating master's fruit (6)
I believe the answer is:
tomato
'fruit' is the definition.
(I've seen this before)
'film dog eating master's' is the wordplay.
'film dog' becomes 'toto' (dog from The Wizard of Oz).
'eating' means one lot of letters goes inside another.
'master' becomes 'ma'.
'toto' going around 'ma' is 'TOMATO'.
(Other definitions for tomato that I've seen before include "A motto turned out to be fruit or veg" , "In France, it's a love apple" , "Pulpy fruit eaten as vegetable" , "A motto turned out to be fruit/veg" , "Red fruit eaten as veg" .)