Medical man investing in a foreign currency (5)
I believe the answer is:
dinar
'foreign currency' is the definition.
(I've seen this before)
'medical man investing in a' is the wordplay.
'medical man' becomes 'dr' (Dr is an example).
'investing' means one lot of letters goes inside another (inserted letters are taken in or invested).
'in'+'a'='ina'
'dr' going around 'ina' is 'DINAR'.
(Other definitions for dinar that I've seen before include "Currency of several Arab countries" , "money" , "Monetary unit of several Arab countries" , "Currency of several Arab states" , "Middle Eastern currency" .)