Toxic shock after ecstasy is unusual (6)
I believe the answer is:
exotic
'unusual' is the definition.
(I've seen this before)
'toxic shock after ecstasy' is the wordplay.
'shock' indicates anagramming the letters (a shocked or disturbed version of the letters).
'after' says to put letters next to each other.
'ecstasy' becomes 'E' (informal term for the drug).
'toxic' with letters rearranged gives 'xotic'.
'xotic' after 'e' is 'EXOTIC'.
'is' is the link.
(Other definitions for exotic that I've seen before include "Colourful or unusual, perhaps from abroad" , "Interestingly different or strange" , "Alluringly foreign" , "Strange, rare or foreign" , "Foreign; glamorous" .)