Dean regularly absorbed by obscure material (5)
I believe the answer is:
denim
'material' is the definition.
(denim is a kind of material)
'dean regularly absorbed by obscure' is the wordplay.
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
'absorbed by' is an insertion indicator.
'obscure' becomes 'dim' (I've seen this before).
The alternating letters of 'dean' are 'en'.
'en' inserted inside 'dim' is 'DENIM'.
(Other definitions for denim that I've seen before include "dark blue material" , "Tough cotton fabric" , "Material for casual trousers or jackets" , "Fabric used for jeans" , "Durable material" .)