Large amount of stone (3)
I believe the answer is:
ton
'large amount' is the definition.
(I've seen this in another clue)
'of stone' is the wordplay.
'of' indicates a hidden word.
'TON' is hidden within 'stone'.
(Other definitions for ton that I've seen before include "A slang 100mph - heavy" , "Speed" , "2240 Ibs" , "Unit of weight equivalent to 2240 pounds" , "2,240 lbs" .)