Herbivore gets drunk on tequila primarily taking too many drugs (9)

I haven't cracked this one yet — but the brilliant team at Fifteensquared have:

*(GETS) + OD (=too many drugs, i.e. overdose) + ON + T <equila> (“primarily” means first letter only); “drunk” is the anagram indicator; the stegodont is an extinct mammal with ridged teeth, related to the mastodon and the elephant