Large honour for hanger-on (4)
I believe the answer is:
lobe
'hanger-on' is the definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.
'large honour' is the wordplay.
'large' becomes 'L' (eg in clothes sizes).
'honour' becomes 'obe' (Order of the British Empire award).
'l'+'obe'='LOBE'
'for' acts as a link.
Can you help me to learn more?
(Other definitions for lobe that I've seen before include "flap" , "Fleshy part of the ear (4)" , "part of brain" , "Part of ear or leaf" , "Rounded part (of organ)" .)