Hanger-on brings nobleman honour (7)
I believe the answer is:
earlobe
'hanger-on' is the definition.
Although both the answer and definition are singular nouns, I cannot see how one could define the other.
'nobleman honour' is the wordplay.
'nobleman' becomes 'earl' (member of the nobility).
'honour' becomes 'OBE' (Order of the British Empire).
'earl'+'obe'='EARLOBE'
'brings' acts as a link.
Can you help me to learn more?
(Other definitions for earlobe that I've seen before include "It depends on the listener" , "Flap on the side of the head" , "something of a listener" , "Often-pierced flap" , "that could have a ring to it" .)