Finally, "Hi ho Silver" before the charge! (4)
I believe the answer is:
agio
'the charge' is the definition.
(term used in currency exchange)
'finally hi ho silver before' is the wordplay.
'finally' indicates one should take the final letters.
'silver' becomes 'ag' (Ag is the chemical symbol for silver).
'before' means one lot of letters go next to another.
The final letters of 'hi ho' are 'io'.
'io' after 'ag' is 'AGIO'.
(Other definitions for agio that I've seen before include "... what would you give to exchange" , "Discount" , "Money-changing" , "Transfer fee" , "Sum payable" .)