Mineral that's "fine" provided by dodgy pedlars (8)
I believe the answer is:
feldspar
'mineral' is the definition.
(feldspar is a kind of mineral)
'fine provided by dodgy pedlars' is the wordplay.
'fine' becomes 'f' (abbreviation).
'provided by' means one lot of letters go next to another.
'dodgy' indicates anagramming the letters.
'pedlars' with letters rearranged gives 'eldspar'.
'f'+'eldspar'='FELDSPAR'
'that's' acts as a link.
(Other definitions for feldspar that I've seen before include "Raw material used in glass-making, ceramics etc - red flaps (anag)" , "Common mineral" , "Rock producer" , "crystal" , "Large wading bird" .)