Domain of actual money (5)
I believe the answer is:
realm
'domain' is the definition.
(I've seen this before)
'actual money' is the wordplay.
'actual' becomes 'real' ('real' can be a synonym of 'actual').
'money' becomes 'm' (abbreviation in economics).
'real'+'m'='REALM'
'of' acts as a link.
(Other definitions for realm that I've seen before include "Province" , "Area of influence" , "Empire - state" , "Monarchy" , "Kingdom, domain" .)