American with ale gut developed fundamental muscle? (8)

I believe the answer is:

glutaeus

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

'fundamental muscle?' is the definition.
I don't know anything about this answer so I can't judge whether it can be defined by this definition.

'american with ale gut developed' is the wordplay.
'american' becomes 'us' (United States).
'with' is a charade indicator (letters next to each other).
'developed' is an anagram indicator.
'ale'+'gut'='alegut'
'alegut' is an anagram of 'glutae'.
'us' after 'glutae' is 'GLUTAEUS'.

Can you help me to learn more?

I've seen this clue in The Independent.

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.