Poet initiates an uncommonly dense epic narrative (5)
I believe the answer is:
auden
'poet' is the definition.
(WH Auden, 1907-1973)
'initiates an uncommonly dense epic narrative' is the wordplay.
'initiates' indicates taking the first letters (I've seen 'initiated' mean this).
The first letters of 'an uncommonly dense epic narrative' is 'AUDEN'.
(Other definitions for auden that I've seen before include "British-born writer" , "British-born American poet" , "Wystan Hugh -, poet" , "W. H. -, Eng. poet" , "W. H. -, English-born poet" .)