Clattering, making or filled with a clattering sound.
I hear the hoofs a-clatter.1907, W. B. Yeats, Deirdre, London: A. H. Bullen, page 9:
It ain’t an easy job, directing traffic at ’Yde Park Corner. Buses and ’ansom cabs. All a-clatter on the cobbles.1941, Virginia Woolf, Between the Acts, London: The Hogarth Press, published 1965, page 188:
2 more examples
The Biarritz [Hotel in San Sebastián] is always remembered by us for its beguilingly venerable lobby aclatter with no less than 82 clocks whose ticks, tocks, cuckoos, roosters, and chimes will keep your ears buzzing until you’ll wish tempus wouldn’t fugit.1968, Temple Fielding, Fielding’s Travel Guide to Europe, New York: Fielding Publications, page 1126:
Her long, black hair in four braids, snaking around her head, pink plastic barrettes aclatter, she flew across the park […]2005, Peter Rock, The Bewildered, San Francisco: MacAdam/Cage, Part 2, Chapter 15, p. 167:
aclatter
adv
Etymology From a- + clatter.
1
Clattering, with a clatter.
The wet sack collapsing aclatter on the ground.1979, Cormac McCarthy, Suttree, New York: Vintage, page 455: