Tasteless dwelling from 1900 soon occupied by Spanish agreement (9)

I believe the answer is:

mcmansion

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

'tasteless dwelling' is the definition.
The definition suggests a singular noun which matches the answer.

'1900 soon occupied by spanish agreement' is the wordplay.
'1900' becomes 'mcm' (I've seen this in another clue).
'soon' becomes 'anon' (synonyms).
'occupied by' indicates putting letters inside (inserted letters occupy or enter the word).
'spanish agreement' becomes 'si' (Spanish for yes).
'anon' going around 'si' is 'ansion'.
'mcm'+'ansion'='MCMANSION'

'from' is the link.

Can you help me to learn more?

I've seen this clue in The Times.

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.