Get rid of 500 yen (5)
I believe the answer is:
ditch
'get rid' is the definition.
(I've seen this before)
'500 yen' is the wordplay.
'500' becomes 'd' ('d' can be a synonym of '500').
'yen' becomes 'itch' (I've seen this before).
'd'+'itch'='DITCH'
'of' is the link.
(Other definitions for ditch that I've seen before include "Throw away (sl.)" , "Forsake" , "Narrow channel" , "side of field?" , "Moat" .)