Place to store dead old form of currency (6)
I believe the answer is:
crypto
'form of currency' is the definition.
I know nothing about this answer so I can't judge whether it can be defined by this definition.
'place to store dead old' is the wordplay.
I cannot quite understand how this works, but
'place' could be 'crypt' (crypt is a kind of place) and 'crypt' is found in the answer.
'old' could be 'o' (common abbreviation eg in OE for Old English) and 'o' is found in the answer.
This accounts for all the letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for crypto that I've seen before include "closet" , "Prefix denoting hidden or obscure" .)