Foreign currency some purchased in Arabia (5)
I believe the answer is:
dinar
'foreign currency' is the definition.
(I've seen this before)
'some purchased in arabia' is the wordplay.
'some' indicates the answer is hidden within the clue (some of the parts of the word are used).
'DINAR' is hidden within 'purchased in arabia'.
(Other definitions for dinar that I've seen before include "Monetary unit of several Arab countries" , "Currency of Algeria, Tunisia, Kuwait etc" , "Currency unit of Algeria, Libya etc" , "Currency of several Arab countries" , "Iraqi capital" .)