The headword a)elpe/wn is similarly glossed in ps.-Zonaras, i.e. in a way which shows that it is a present participle in the masculine nominative singular. (Adler reports the same entry in the Ambrosian Lexicon.) Evidently quoted from somewhere, but not independently attested.
The verb a)elpe/w appears to be a rare variant of a)elpte/w (for which see LSJ s.v.).