Quite liked this, but you really need to work on your allowable answers. Synonym should be accepted, for example, and singular terms are easily allowed simply by not putting the s on in your answer grid.

Clever red herrings! The link for spliff group should also accept marjuana, not just cannabis.

Hey Ace, synonyms was there as an acceptable answer, I won't bother pluralising in the future. Hey Logophile, the other acceptable answer was slang terms for a cannabis cigarette, I didn't include marijuana or ganga or pot because they're all slang terms as well, but simply typing slang would've got you the point, the system isn't perfect.