Cheek of learner I park behind! (3)
I believe the answer is:
lip
'cheek' is the definition.
(both can mean insolence or rudeness)
'learner i park behind' is the wordplay.
'learner' becomes 'l'.
'i park' becomes 'ip' (this could be a standard abbreviation which I don't know about).
'behind' is a charade indicator (letters next to each other).
'l'+'ip'='LIP'
'of' acts as a link.
Can you help me to learn more?
(Other definitions for lip that I've seen before include "giving such insincere service" , "Part of mouth or cheek" , "Brink" , "Rim of an orifice" , "Edge, rim" .)