Figure Homer represented eating butter up (8)
I believe the answer is:
metaphor
'figure' is the definition.
(figure of speech)
'homer represented eating butter up' is the wordplay.
'represented' indicates anagramming the letters.
'eating' means one lot of letters goes inside another.
'butter' becomes 'pat' (a pat can mean a lump of butter).
'up' says the letters should be written in reverse (in down clue: letters go upwards).
'pat' back-to-front is 'tap'.
'homer' anagrammed gives 'mehor'.
'mehor' enclosing 'tap' is 'METAPHOR'.
(Other definitions for metaphor that I've seen before include "Common figure of speech" , "Analogy" , "Figure of speech that directly indicates a likeness" , "Allegorical figure" , "Captain of industry, eg" .)