Business he thinks should not be a matter of duty (4,6)
I believe the answer is:
free trader
'business he thinks should not be a matter of duty' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'business he' is the wordplay.
I cannot really understand how this works, but
'business' could be 'trade' (trade is a kind of business) and 'trade' is located in the answer.
'he' could be 'free' and 'free' is located in the answer.
A single letter 'r' remains which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for free trader that I've seen before include "Bright" , "Duty-dodger" , "as one whose views are of unrestricted general import" .)