Rum spilt by a learner on the wall! (5)
I believe the answer is:
mural
'the wall' is the definition.
'rum spilt by a learner' is the wordplay.
'spilt' indicates anagramming the letters.
'by' is a charade indicator (letters next to each other).
'learner' becomes 'l'.
'rum' is an anagram of 'mur'.
'mur'+'a'+'l'='MURAL'
'on' acts as a link.
(Other definitions for mural that I've seen before include "Wall design" , "Large wall painting" , "Wall art" , "Drawing on a wall" , "Wall-painting" .)