Poet's cry is lit up (8)
I believe the answer is:
lyricist
'poet's' is the definition.
(thesaurus)
'cry is lit up' is the wordplay.
'up' indicates anagramming the letters (letters get chucked up).
'cry'+'is'+'lit'='cryislit'
'cryislit' with letters rearranged gives 'LYRICIST'.
(Other definitions for lyricist that I've seen before include "Writer of words, as opposed to music" , "Sit Cyril down - he's a songwriter" , "One who writes the words of a song" , "Person who writes words for songs" , "The one who writes the words for songs" .)