Mount or fasten a bath with ring (8)

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

You’ll all remember when this Philippine volcano blew up in 1991, causing a world wide temperature drop with sulphurous mist across most of the stratosphere. Well all right, neither did I, constructing it from likely guesses on the wordplay – fasten: PIN, A, bath: TUB and ring: O – and checking its existence.