Old money collection hidden among vegetables (7)
I believe the answer is:
pesetas
'old money' is the definition.
(former currency of Spain)
'collection hidden among vegetables' is the subsidiary indication.
'collection' becomes 'set' (set is a kind of collection**).
'hidden among' indicates putting letters inside.
'vegetables' becomes 'peas' (I've seen this before).
'set' inserted into 'peas' is 'pesetas'.
(Other definitions for pesetas that I've seen before include "cash, once" , "Old Spanish money" , "Spanish bread no longer used" , "Units of Spanish money" , "old bread" .)