The headword, attested only here, is the present active participle, feminine nominative (and vocative) singular, of the verb suneyia/zw, a variant of suneyia/w, I play along with, together; see generally LSJ s.v. It is evidently generated from the quotation given, where the uncontracted form suneyia/ousa of the aforementioned verb occurs [In her critical apparatus Adler reports that ms A lacks this entry.]
[1] The gloss is the present active participle, feminine nominative (and vocative) singular, of the compound verb sumpai/zw, I play along with like a child, I sport along with; see generally LSJ s.v.
[2] Greek Anthology 5.288.1 (Paulus Silentiarius), on an obsessive passion. Khariklo (Chariclo) was the name of two characters in Greek mythology: the wife of Chiron the centaur (cf. kappa 1107 n. 2) and the mother of T(e)iresias (tau 453). [In her critical apparatus Adler reports that mss FG here transmit the variant spelling of the participle.]