It smooths over part of minor incident, on reflection (4)
I believe the answer is:
iron
'it smooths over' is the definition.
'part of minor incident on reflection' is the wordplay.
'part of' says the answer is hidden in the clue.
'on reflection' shows that the letters should be reversed in order.
'nori' is hidden within 'minor incident'.
'nori' written backwards gives 'IRON'.
(Other definitions for iron that I've seen before include "The metallic element plays a role in the transport of oxygen by the blood" , "Smooth things" , "Main component of steel" , "Smooth - press - club" , "Press clothes" .)