Scam involving excessive material (6)
'material' is the definition.
(cotton is a kind of material)
'scam involving excessive' is the wordplay.
'scam' becomes 'con' (I've seen this before).
'involving' indicates putting letters inside.
'excessive' becomes 'ott' (short for 'over the top' - informal British).
'con' going around 'ott' is 'COTTON'.
(Other definitions for cotton that I've seen before include "Kind of thread or fabric" , "Fabric made from tropical plant - old man river don't plant it" , "Soft white substance used to make fabric - in song, Old Man River don't plant it" , "Fabric woven from plant fibres" , "Plantation product" .)
But I've got no explanation for this one! Could you help me understand?
(Other definitions for swedes that I've seen before include "Root vegetables" , "Europeans and turnips" , "Turnips from Scandinavia?" , "Turnips for Scandinavians" .)