The headword -- evidently extracted from somewhere -- is attested only in lexicography and with this accentuation only in the Suda. It is apparently the extrapolation of a present active participle, in the feminine nominative (and vocative) singular, from a Doric or Aeolic substantive (cf. sigma 41, with corresponding gloss); cf. sigma 58.
[1] The gloss is the present active participle, feminine nominative (and vocative) singular, of the verb fronti/zw, I consider, take thought, feel concern; see generally LSJ s.v. The headword (but for the difference in its accentuation) is identically glossed in Hesychius (sigma122) and in Photius' Lexicon (sigma52 Theodoridis).
[2] A similar gloss is given at sigma 41; cf. Synagoge s.v. sa/los, and Photius loc.cit.