Drug that makes you go wild I tried outside upper-class clubs (8)

'drug' is the definition.
(diuretic is a kind of drug)

'go wild i tried outside upper-class clubs' is the wordplay.
'go wild' is an anagram indicator (I've seen 'going wild' mean this).
'outside' is a charade indicator (letters next to each other) (outside can mean adjacent to).
'upper class' becomes 'u' (as in U- and non-U speech).
'clubs' becomes 'c' (abbreviation used in card games such as bridge).
'i'+'tried'+'u'='itriedu'
'itriedu' with letters rearranged gives 'diureti'.
'diureti'+'c'='DIURETIC'

'that makes you' acts as a link.