Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
monstrātĭo, ōnis, f. [monstro], a showing, direction (only in Terence and Vitruv.): defessus sum ambulando: ut, Syre, te cum tuā Monstratione magnus perdat Juppiter, direction, Ter. Ad. 4, 6, 1: solers et expedita monstratio, indication, hint, Vitr. 6, 1, 12.