Difficult end endured without drug (8)
I believe the answer is:
stubborn
'difficult' is the definition.
(I've seen this before)
'end endured without drug' is the wordplay.
'end' becomes 'stub' (I've seen this before**).
'endured' becomes 'borne' (I've seen this before).
'without' is a deletion indicator.
'drug' becomes 'e' (e is another name for ecstasy).
'borne' with 'e' taken away is 'born'.
'stub'+'born'='STUBBORN'
(Other definitions for stubborn that I've seen before include "Wilful" , "Obstinate, unwilling to yield" , "Unwilling to yield or grant a point" , "Obstinate, unyielding" , "Inflexible" .)