In Venetian dialect 'brusa la vecia' means 'burn the old woman'. Then, alongside the handsome gateway to the Arsenale I saw this effigy suspended in the sunshine:
A spot of online research reveals that the custom of burning the effigy of a hag is widespread in northern Italy, or at least in the northeast, where it most commonly takes place at Epiphany (6th January). I did find one reference to the tradition of celebrating 'Metà Quaresima' - half-Lent - in a similar fashion:
> Festivals of Italy
Even a local Venetian friend wasn't very well-up on this event, though making the good suggestion that it resembled a pagan 'farewell to winter' celebration.
So I turned up in the evening and found a very local event - mostly families from the local parish, standing and chatting or dancing with children as a man sang Italian standards with a microphone over recorded music. Punctually at 7:30pm, without much fanfare, as the singer emoted through Te voglio bene assai, the dangling figure was ignited and proceeded to burn merrily as the onlookers clustered around, with fragments of burning material spiralling up above our heads.
Then the effigy burned away, a female singer took over on the little stage with a song dedicated to a local little girl, and the little crowd returned to chatting, drinking an ombra and eating the snacks provided. One possibly inebriated old man in a woollen hat swayed as he blew kisses to the singer. There was an announcement about 'again this time next year', and the drama was over.
So if you are in Venice halfway through Lent in the future, I'd suggest heading to the Arsenale to see what you find.