King with currency (4)
I believe the answer is:
rand
'currency' is the definition.
(I've seen this before)
'king with' is the wordplay.
'king' becomes 'R' (abbreviation for rex, king in Latin).
'with' becomes 'and'.
'r'+'and'='RAND'
(Other definitions for rand that I've seen before include "Currency of South Africa" , "Foreign currency" , "our 1/4 Across [GOLD MEDALLIST] in 1964" , "South African currency unit" , "South African money" .)