Plant of the genus Nepeta also called catmint (6)
I believe the answer is:
catnip
(Other definitions for catnip that I've seen before include "Plant with scented leaves which felines like" , "Hairy aromatic perennial herb strongly attractive to some pets" , "Herb of the mint family, attractive to some pets" , "treat for moggie" , "Plant favoured by felines" .)