Soporific plant left world leader losing power (5)

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

Soporific plant left world leader losing power L (=left) + <p> OTUS (=world leader, i.e. President of the United States; “losing power (=P, in physics)” means letter “p” is dropped); cf. the Lotus-eaters, from the Odyssey