Imported vaccine in the end’s toxic preparation (6)
I believe the answer is:
exotic
'imported' is the definition.
(thesaurus)
'vaccine in the end's toxic preparation' is the wordplay.
'in the end's' indicates one should take the final letters (I've seen 'in the end' mean this).
'preparation' indicates anagramming the letters.
The last letter of 'vaccine' is 'e'.
'toxic' with letters rearranged gives 'xotic'.
'e'+'xotic'='EXOTIC'
(Other definitions for exotic that I've seen before include "Foreign, strange or exciting" , "Weird; alien" , "Foreign; strikingly colourful" , "Foreign; glamorous" , "Having a strange beauty" .)