Adjust fee or tax cash for currency charge (4,2,8)
I believe the answer is:
rate of exchange
'currency charge' is the definition.
'rate of exchange' can be an answer for 'charge' (rate of exchange is a kind of charge). I'm not certain of the 'currency' bit.
'adjust fee or tax cash' is the wordplay.
'adjust' is an anagram indicator.
'cash' becomes 'change' (change is a kind of cash).
'fee'+'or'+'tax'='feeortax'
'feeortax' is an anagram of 'rateofex'.
'rateofex'+'change'='RATE OF EXCHANGE'
'for' is the link.
Can you help me to learn more?
(Other definitions for rate of exchange that I've seen before include "speed one bargains?" , "Get it for a few pounds" .)