= Photius sigma125 Theodoridis, but with some substantial variations (see n. 2 below).
The headword is the aorist active infinitive of the verb sei/w, which in other contexts means simply 'shake' (cf. sigma 289, sigma 291, sigma 292). With the specialized meaning given here (LSJ s.v. sei/w, 4), the only attestation of this particular form of the verb is in the fragment of Telecleides given below (n. 2); but something like this connotation is attested in other forms of the verb. In addition to the fragment from Aristophanes' Banqueters given below (n. 3) see Aristophanes, Knights 840 (participle), Antiphon 6.45 (imperfect indicative), though the precise meaning in these cases seems to be more along the lines of 'extort by threatening to inform'.
[1] = Hesychius sigma353, Synagoge sigma45; cf. Photius sigma111 and Hesychius sigma330, which Theodoridis compares to a scholion on Aristophanes, Knights 840.
[2] Teleclides fr. 2 Kock (and Kassel-Austin). The translation here represents as much sense as can be made of the Suda's text, which is probably the result of a transcription from oral dictation by someone who did not understand what he was writing. Theodoridis' text of Photius sigma125 is more coherent as a result of the adoption of a number of Porson's conjectures. Kock, Edmonds and Kassel-Austin, with the help of an additional conjecture by Porson derived from Suda ms E (ante correctionem), print what is the most likely reading: a)/ll' w)= pa/ntwn a)stw=n lw=|stoi sei=sai kai\ proskale/sasqai, pau/sasqe dikw=n a)llhlofa/gwn ("but, o best of all citizens at giving the shakedown and serving summonses, refrain from cannibalistic lawsuits.")
[3] Aristophanes fr. 219 Kock (and Edmonds), 228 Kassel-Austin. (Banqueters is only preserved in fragments.) The text here is also that presented by Theodoridis (Photius sigma125) and Kassel-Austin's text of the fragments. Kock and Edmonds follow Dindorf in omitting the pa/lin. Küster (followed by Porson in his edition of Photius) transposed the last two words so that the quotation might consist of one entire iambic trimeter and the beginning of a second. The alternatives (whether with or without the pa/lin) do not fit into standard trimeters.