Strangely pure English currency (5)
I believe the answer is:
rupee
'currency' is the definition.
(eg currency of India)
'strangely pure english' is the wordplay.
'strangely' indicates an anagram.
'english' becomes 'E' (abbreviation).
'pure' is an anagram of 'rupe'.
'rupe'+'e'='RUPEE'
(Other definitions for rupee that I've seen before include "Currency of the subcontinent" , "little money abroad" , "Indian money unit" , "foreign money" , "Unit of money in India" .)