Pity has transformed yours truly (5)
I believe the answer is:
shame
'pity' is the definition.
(I've seen this before)
'has transformed yours truly' is the wordplay.
'transformed' indicates anagramming the letters.
'yours truly' becomes 'me'.
'has' is an anagram of 'sha'.
'sha'+'me'='SHAME'
(Other definitions for shame that I've seen before include "Disgrace - Salman Rushdie novel" , "Painful emotion resulting from guilt" , "disgraceful" , "scandal" , "pity!" .)