Queen on currency charge (6)
I believe the answer is:
errand
'charge' is the definition.
(I've seen this before)
'queen on currency' is the wordplay.
'queen' becomes 'er' (abbreviation for Elizabeth Regina).
'on' means one lot of letters go next to another.
'currency' becomes 'rand' (I've seen this before).
'er'+'rand'='ERRAND'
(Other definitions for errand that I've seen before include "Useful journey" , "Mission (often run)" , "A short journey to deliver orget goods" , "Short journey on behalf of another" , "Native of a former German kingdom" .)