Drug Emma, suffering with the pain (11)
I believe the answer is:
amphetamine
'drug' is the definition.
(amphetamine is a kind of drug)
'emma suffering with the pain' is the wordplay.
'suffering with' indicates anagramming the letters.
'the'+'pain'='thepain'
'emma' with its letters mixed up with 'thepain' gives 'AMPHETAMINE'.
(Other definitions for amphetamine that I've seen before include "Stimulant drug" , "Upper" , "speed that's restricted by law" , "Mood-altering drug" .)