The headword is the present middle/passive participle, either masculine accusative singular or neuter nominative/accusative singular, of the verb thmele/w, I look after; cf. alpha 3450 (gloss), tau 503, tau 504, tau 505, and see generally LSJ s.v. It must be extracted from somewhere, unidentifiable. (Not Palladius, Historica Lausiaca, vita 24.2.5 (Cunningham, p. 470n), if the lemma is correctly regarded as originating with Phrynichus: Praeparatio sophistica fr. 360.)
[1] The glosses are the same form as the headword, but from the verbs e)pimele/omai (I take care of) and filokale/w (I love the beautiful, am enthusiastic for, put in good order), respectively; see generally LSJ s.vv. Besides Phrynichus (see preceding note), the headword is identically glossed by Photius' Lexicon, Lexica Segueriana 387.5, and the Synagoge; cf. Hesychius s.v. thmelh=sai (tau 505).