Scam importing excessive material (6)
I believe the answer is:
cotton
'material' is the definition.
(cotton is a kind of material)
'scam importing excessive' is the wordplay.
'scam' becomes 'con' (I've seen this before).
'importing' is an insertion indicator.
'excessive' becomes 'ott' (short for 'over the top' - informal British).
'con' enclosing 'ott' is 'COTTON'.
(Other definitions for cotton that I've seen before include "Plant, its fibres for yarn" , "Natural cloth" , "Kind of thread or fabric" , "Plant fibre for fabrics" , "This wool is a fluffy wadding" .)