The headword is the masculine accusative singular or neuter nominative/vocative/accusative singular of the adjective strufno/s, -h/, -o/n; see generally LSJ s.v. It is presumably (though not demonstrably) extracted from the quotation given, where it is neuter accusative.
[1] The gloss is the same grammatical form of the adjective sklhro/s, -a/, -o/n; see generally LSJ s.v. Note also Photius, Lexicon sigma644, which, as transmitted, glosses strufo/n (obelized by Theodoridis and his predecessors as a vox nihili) with strufno/n and sklhro/n.
[2] An approximation of Aristophanes, Wasps 877 (web address 1): Bdelycleon ("Loathes Kleon") prays to Apollo Agyieus (Mikalson, p. 135) for a change in the courtroom demeanor of his father Philocleon ("Loves Kleon"). [For Kleon (Develin person no. 1659) cf. OCD4 s.v. Cleon, and kappa 1731.]