Charge less than a French trader initially taking in the German copper (8)
I believe the answer is:
undercut
'charge less than' is the definition.
(I've seen this before)
'a french trader initially taking in the german copper' is the wordplay.
'a french' becomes 'un' ('a' in French).
'trader initially' becomes 't' (I can't justify this - if you can you should give a lot more credence to this answer).
'taking in' is an insertion indicator.
'the german' becomes 'der' ('the' in German).
'copper' becomes 'Cu' (Cu is the chemical symbol for copper).
'un'+'t'='unt'
'der'+'cu'='dercu'
'unt' going around 'dercu' is 'UNDERCUT'.
Can you help me to learn more?
(Other definitions for undercut that I've seen before include "Weaken, undermine" , "Offer goods at a lower price to beat a competitor" , "strike" , "Weaken - part of a sirloin of beef" , "Sell for lower price than another" .)