Down 15. Treat one and get it wrong about influenza, ultimately (9)
My across answers (hopefully correct) give me
N _ G _ T _ A _ E
And the only possible words I can see are NIGHTMARE and NEGOTIATE. (I've now checked these with the help of the Quick Solver on this site).
I'm guessing "Negotiate"
GET IT "wrong" = EGOTI
Influenza, ultimately = A
But that's it for me. N T E ?
Am I pub monarch up the wrong tree?