Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
sŭbēlectĭo, ōnis, f. [sub-eligo], a further selection (late Lat.): subelectio est quando de bonis electis eliguntur meliores, Ps.Aug. ad Frater. Erem. Serm. 39.