Ugly bun baked with sweetheart approaching (10)

I believe the answer is:

unbecoming

I'm a little stuck... Click here to teach me more about this clue!

'ugly' is the definition.
Both the answer and definition are adjectives. Maybe there's a link between them I don't understand?

'bun baked with sweetheart approaching' is the wordplay.
'baked with' indicates an anagram.
'sweetheart' becomes 'e' (the middle letter or heart of 'sweet').
'approaching' becomes 'coming' (synonyms).
'bun' anagrammed with 'e' gives 'unbe'.
'unbe'+'coming'='UNBECOMING'

Can you help me to learn more?

(Other definitions for unbecoming that I've seen before include "Indelicate" , "Not flattering or fitting" , "Not flattering; unseemly" , "indecorous" , "inappropriate" .)

I've seen this clue in the Sydney Morning Herald.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.