Proposition from her to me (7)
I believe the answer is:
theorem
'proposition' is the definition.
(I know that theorem is a type of proposition)
'from her to me' is the wordplay.
'from' is an anagram indicator (the anagram comes from the same letters).
'her'+'to'+'me'='hertome'
'hertome' anagrammed gives 'THEOREM'.
(Other definitions for theorem that I've seen before include "mathematical achievement" , "The more it changed to a proposition to be proved" , "Mathematical statement to be proved" , "speculation" , "deduction" .)