The French way to get fat (4)
I believe the answer is:
lard
'fat' is the definition.
(lard is a kind of fat)
'the french way' is the wordplay.
'the french' becomes 'la'.
'way' becomes 'rd' (**).
'la'+'rd'='LARD'
'to get' is the link.
(Other definitions for lard that I've seen before include "Pork fat" , "Pig-fat" , "stuff with bacon" , "Aggrandise - embellish" , "F [FAT]" .)