Rubbish drug experience on ecstasy (5)
I believe the answer is:
tripe
'rubbish' is the definition.
(both can mean nonsense)
'drug experience on ecstasy' is the wordplay.
'drug experience' becomes 'trip' (as in tripping on drugs).
'on' says to put letters next to each other (in a down clue, letters appear on others).
'ecstasy' becomes 'E' (informal term for the drug).
'trip'+'e'='TRIPE'
(Other definitions for tripe that I've seen before include "Lining of the stomach of a cow as food" , "What some northerners eat" , "Balderdash" , "Rubbish; stomach as food" , "Rot" .)