Material used in packaging hamburgers (7)
I believe the answer is:
gingham
'material' is the definition.
(gingham is a kind of material)
'in packaging hamburgers' is the wordplay.
'in' says the answer is hidden in the clue.
'GINGHAM' is hidden in the letters of 'packaging hamburgers'.
'used' acts as a link.
(Other definitions for gingham that I've seen before include "Checked material" , "Light cotton checked fabric" , "Fabric in a plaid weave" , "Cotton cloth, maybe checked" , "Lightweight cotton fabric" .)