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 they are linked in a way I don't understand?
'toes at curled up the day after' is the wordplay.
'curled' indicates an anagram (letters curl or twist around).
'up the day' becomes 'd' (I am not sure about this - if you are sure you should believe this answer much more).
'after' says to put letters next to each other.
'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" .)