Money said to be in hidden store (5)
I believe the answer is:
cache
'hidden store' is the definition.
(I've seen this in another clue)
'money said to be' is the wordplay.
'money' becomes 'cash' (cash is a type of money).
'said to be' shows a homophone (sound like).
'cash' sounds like 'CACHE'.
'in' is the link.
(Other definitions for cache that I've seen before include "Hiding place for treasure etc" , "Hidden storage space" , "Stockpile" , "Secretly keep" , "Conceal" .)