Colour rises after one is briefly impolite about guiding principle (6)
I believe the answer is:
rudder
'guiding principle' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how they can define each other.
'colour rises after one is briefly impolite' is the wordplay.
'colour' becomes 'red' (red is a kind of colour).
'rises' shows that the letters should be reversed in order.
'after' says to put letters next to each other.
'one is briefly' means to remove the last letter.
'impolite' becomes 'rude' (similar in meaning).
'red' written backwards gives 'der'.
'rude' with its last letter taken off is 'rud'.
'der' after 'rud' is 'RUDDER'.
'about' acts as a link.
Can you help me to learn more?
(Other definitions for rudder that I've seen before include "Boat steering surface" , "Ship's steering plate" , "Something used for steering" , "Boat steerer" , "Steering device on boat" .)