Disease rampant on the way in alien world (9)

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

POX (disease) reversed [rampant] + LANE (way) contained by [in] ET (alien). A planet which orbits a star outside the solar system. I didn’t know this although it has come up on a couple of previous occasions 7 or 8 years ago.