Fat boy suppressing resistance (4)
I believe the answer is:
lard
'fat' is the definition.
(I know that lard is a type of edible fat)
'boy suppressing resistance' is the wordplay.
'boy' becomes 'lad' (informal term for boy).
'suppressing' indicates putting letters inside.
'resistance' becomes 'r' (electronics abbreviation).
'lad' going around 'r' is 'LARD'.
(Other definitions for lard that I've seen before include "Fat Scottish landowner appears disheartened" , "White cooking fat" , "Pig-fat" , "Animal fat" , "Pork fat" .)