Grass up gutless editor, a drunkard (5)
I believe the answer is:
toper
'a drunkard' is the definition.
(I've seen this in another clue)
'grass up gutless editor' is the wordplay.
'grass' becomes 'pot' (cannabis).
'up' says the letters should be written in reverse (in down clue: letters go upwards).
'gutless' says to hollow out the word (remove centre letters).
'editor' with its middle taken out is 'er'.
'pot' back-to-front is 'top'.
'top'+'er'='TOPER'
(Other definitions for toper that I've seen before include "Alcoholic" , "boozer" , "Excessive drinker" , "Lush" , "Drinker, imbiber" .)