Vassal for example tucking into pork pie (5)
I believe the answer is:
liege
'vassal' is the definition.
('liege' can be a synonym of 'vassal')
'example tucking into pork pie' is the wordplay.
'example' becomes 'eg'.
'tucking into' indicates putting letters inside.
'pork pie' becomes 'lie' (I've seen this in other clues).
'eg' going into 'lie' is 'LIEGE'.
'for' is the link.
(Other definitions for liege that I've seen before include "Belgian city on Meuse" , "City in eastern Belgium" , "Sort of lord" , "Large Belgian city" , "European city" .)