Quite enjoying this after the brain-shredding exercises of the last two Listeners.
I almost have a full grid but cannot make anything sensible out of 23ac "Volcano lava erupting, covering previous flow (6)".
Assuming my crossers are correct, which I'm reasonably confident of, Chambers gives me two possibilities for the entry but neither seems to fit the clue.
As ever, a gentle prod in the right direction would be highly appreciated!