Husband goes berserk on ecstasy in Asian capital (8)

'asian capital' is the definition.
(capital of Tajikistan)

'husband goes berserk on ecstasy' is the wordplay.
'goes berserk' is an anagram indicator.
'on' is a charade indicator (letters next to each other).
'ecstasy' becomes 'E' (informal term for the drug).
'husband' with letters rearranged gives 'dushanb'.
'dushanb'+'e'='DUSHANBE'

'in' is the link.