Lump of gold ore (6)
I believe the answer is:
nugget
'lump of gold ore' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for nugget that I've seen before include "Piece of gold, information" , "Small lump of gold" , "Piece of precious metal (or chicken?)" , "Lump of, eg, gold" , "Lump of metal, say gold" .)