Briefly handle certain wealth stored up (8)
I believe the answer is:
treasure
'wealth stored up' is the definition.
(I've seen this before)
'briefly handle certain' is the wordplay.
'briefly' means to remove the last letter.
'handle' becomes 'treat' (synonyms).
'certain' becomes 'sure' (synonyms).
'treat' with its final letter taken off is 'trea'.
'trea'+'sure'='TREASURE'
(Other definitions for treasure that I've seen before include "Hoarded riches" , "Valuable hoard" , "Valued possession, buried perhaps" , "Quantity of precious objects" , "X marks its spot!" .)