How to interpret old money (7)
I believe the answer is:
expound
'how to interpret' is the definition.
I can't judge whether this definition defines the answer.
'old money' is the wordplay.
'old' becomes 'ex' (prefix meaning former or onetime).
'money' becomes 'pound' (pound sterling).
'ex'+'pound'='EXPOUND'
Can you help me to learn more?
(Other definitions for expound that I've seen before include "Upend ox (anag)" , "Explain and interpret" , "Elucidate" , "Explain meaning in detail" , "Set forth, explain in detail" .)