She's quite angry in the morning (5)

I believe the answer is:

madam

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

'she's quite' is the definition.
I can't tell whether this defines the answer.

'angry in the morning' is the wordplay.
'angry' becomes 'mad' (similar in meaning).
'in the morning' becomes 'am' (AM on a clock).
'mad'+'am'='MADAM'

Can you help me to learn more?

(Other definitions for madam that I've seen before include "'Call Me ---' (I. Berlin)" , "Woman of standing" , "Courteous form of address to a woman" , "Formal address to a woman - precocious little girl" , "Woman with status - girl with bad manners" .)

I've seen this clue in the Evening Standard.

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.