Lewis & Short

clancŭlō, adv. (access. form of clanculum) [clam], secretly, privately (postclass.), App. M. 3, p. 133, 5; 9, p. 221, 13; 10, p. 245, 26; Macr. S. 5, 18; Amm. 21, 12, 13; August. Ep. 54.