Poet sadly edgier after depression (9)
I believe the answer is:
coleridge
'poet' is the definition.
(Samuel Taylor Coleridge, 1772-1834)
'sadly edgier after depression' is the wordplay.
'sadly' is an anagram indicator.
'after' is a charade indicator (letters next to each other).
'depression' becomes 'col' (geographical term for a low point).
'edgier' anagrammed gives 'eridge'.
'eridge' after 'col' is 'COLERIDGE'.
(Other definitions for coleridge that I've seen before include "Samuel Taylor . . . . . . . . ., eminent poet" , "Ancient Mariner poet" , "English poet" , "Exponent of art" , "Poet, author of the 9 19" .)