Profoundly deaf elephant enjoyed peaceful later years, initially (6)
I believe the answer is:
deeply
'profoundly' is the definition.
(synonyms)
'deaf elephant enjoyed peaceful later years initially' is the wordplay.
'initially' indicates taking the first letters.
The first letters of 'deaf elephant enjoyed peaceful later years' is 'DEEPLY'.
(Other definitions for deeply that I've seen before include "With intense feeling" , "Thoroughly" , "Profoundly" , "In a profound way" , "With profundity" .)