Ring found amongst solid treasure (5)
I believe the answer is:
hoard
'treasure' is the definition.
(I've seen this before)
'ring found amongst solid' is the wordplay.
'ring' becomes 'O' (letter resembling a ring).
'found amongst' is an insertion indicator (inserted letters are placed amongst others).
'solid' becomes 'hard' (associated in meaning).
'o' going within 'hard' is 'HOARD'.
(Other definitions for hoard that I've seen before include "Store of money or valuables" , "accumulated wealth" , "Collection" , "Accumulation" , "Hard kick" .)