Removal of hard skin from undercoat and its base (12)

I believe the answer is:

decrustation

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

'removal of hard skin' is the definition.
The definition suggests a singular noun which matches the answer.

'undercoat and its base' is the wordplay.
'and' is a charade indicator (letters next to each other).
'base' is an anagram indicator (base can mean impure or corrupt).
'undercoat'+'its'='undercoatits'
'undercoatits' is an anagram of 'DECRUSTATION'.

'from' acts as a link.

Can you help me to learn more?

(Another definition for decrustation that I've seen is " removal of coating on outside".)

I've seen this clue in The Guardian.

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.