Australian in crude Tinder exchange (5,2)
I believe the answer is:
trade in
'exchange' is the definition.
(I know that trade in is a more specific form of the action exchange)
'australian in crude tinder' is the wordplay.
'australian' becomes 'A' (common abbreviation).
'in' is an insertion indicator.
'crude' is an anagram indicator.
'tinder' is an anagram of 'trdein'.
'a' placed into 'trdein' is 'TRADE-IN'.
(Other definitions for trade in that I've seen before include "Second-hand vehicle" , "Get some money back" , "It's given as part payment" , "exchange for second-hand article" , "Article used in part exchange" .)