Provide a detailed account of old money (7)
I believe the answer is:
expound
'provide a detailed account of' is the definition.
(expound can mean to explain or interpret)
'old money' is the wordplay.
'old' becomes 'ex' (prefix meaning former or onetime).
'money' becomes 'pound' (I've seen this in other clues).
'ex'+'pound'='EXPOUND'
(Other definitions for expound that I've seen before include "Set forth, explain in detail" , "Explain and interpret" , "Elaborate" , "Set out in a detailed and learned way" , "Spell out" .)