Dealer in Mercedes, 50% less than new (8)
I believe the answer is:
merchant
'dealer' is the definition.
(I've seen this before)
'mercedes 50 less than new' is the wordplay.
'mercedes' becomes 'merc' (shortened informal term for Mercedes).
'50' suggests halving the letters.
'less' becomes 'rc' (I can't justify this - if you can you should give a lot more credence to this answer).
'new' indicates anagramming the letters.
'merc' with half the letters taken is 'me'.
'than' is an anagram of 'hant'.
'me'+'rc'+'hant'='MERCHANT'
'in' is the link.
Can you help me to learn more?
(Other definitions for merchant that I've seen before include "Ten march (anag.)" , "Businessperson engaged in trade" , "One who buys and sells" , "Broker" , "Retail trader" .)