That clusters; see verb.
1590. Spenser, F. Q., II. ix. 16. In the ayre their clust’ring armie flies.
1610. Shaks., Temp., IV. i. 112. Vines, with clustring bunches growing.
1634. Milton, Comus, 54. His clustering locks With ivy berries wreathed.
1813. Byron, Corsair, III. ii. Spell-bound within the clustering Cyclades!
Hence Clusteringly adv.
