Warmed one's toes at, curled up, the day after (7)
I believe the answer is:
toasted
'warmed one's' is the definition.
The answer and definition can be both related to change as well as being past participle verbs.
Maybe you can see a link between them that I can't see?
'toes at curled up the day after' is the wordplay.
'curled' is an anagram indicator (letters curl or twist around).
'up the day' becomes 'd' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'after' means one lot of letters go next to another.
'toes'+'at'='toesat'
'toesat' is an anagram of 'toaste'.
'toaste'+'d'='TOASTED'
Can you help me to learn more?
(Other definitions for toasted that I've seen before include "grilled" , "Absent Friends may be" , "Heated" , "drank to the happy couple!" , "Cooked; drank health of" .)