Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
nĭtĭdĭuscŭlus, a, um, adj. dim. [nitidus], somewhat more shining (Plautin.): caput, Plaut. Ps. 1, 2, 84.
Hence, adv.: nĭtĭ-dĭuscŭlē, a little more finely, sprucely: ut curer, Plaut. Ps. 3, 1, 8.