Start of last month turning very chilly (4)

I believe the answer is:

iced

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

But I can't explain it at all! Could you help me understand?

(Other definitions for iced that I've seen before include "What cake might be" , "Covered with flavoured sugar topping" , "reduced number of degrees" , "Kept cool" , "Glazed" .)

I've seen this clue in The Times.

Want a hint initially instead of a full solution? Install my app