Are there such days at the end of three months? (5)

I believe the answer is:

ember

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

'end of three months?' is the definition.
(September, November and December)

I cannot understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for ember that I've seen before include "Cryptic question" , "Glowing coal; prayer (Days)" , "One smouldering" , "It glows in dying fire" , "Fire remnant" .)

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.