No vegetarian would swallow such a lie! (4,3)
I believe the answer is:
pork pie
This clue is a double definition.
'no vegetarian would swallow such' is the first definition.
(vegetarians would not eat pork pies)
'a lie' is the second definition.
(pork pie is Cockney rhyming slang for lie)
(Other definitions for pork pie that I've seen before include "That isn't true" , "M eat and pastry dish" , "The type of hat" , "material from Tamworth, say, processed in case" , "Meat product" .)