Verse from writer on crack (6)
I believe the answer is:
poetry
'verse' is the definition.
('poetry' can be a synonym of 'verse')
'writer on crack' is the wordplay.
'writer' becomes 'poe' (Edgar Allan Poe).
'on' means one lot of letters go next to another.
'crack' becomes 'try' (I've seen this in other clues).
'poe'+'try'='POETRY'
'from' is the link.
(Other definitions for poetry that I've seen before include "Literary genre" , "Sonnets, limericks etc" , "The product of Tennyson or Longfellow" , "'The Raven'?" , "Literature in metrical form" .)