Strip of bacon (6)
'strip of bacon' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for rasher that I've seen before include "American fish" , "More impetuous - slice of meat" , "Less considered" , "Thin slice of bacon" , "Less-considered" .)
(Other definitions for lardon that I've seen before include "bit of a roasting" , "Strip of bacon for roasting meat" , "strip of fat" , "chunk of meat" , "Small piece of bacon used in cooking" .)