The headword, a masculine noun in the nominative singular, is an Aristophanic neologism compounded from pra/gmatos (genitive singular of pra=gma, deed, act, legal business) and difa/w (I search after, probe, poke into); see generally LSJ s.v. and Dunbar, p. 678. The entry is generated from an instance of the headword in the quotation given. Possible translations of it, besides the ones given above, are poker-about after lawsuits (Dunbar) and lawsuit-snoop (Henderson).
cf. omega 79.
[1] The gloss -- from Aristophanic scholia: see next note -- is a masculine noun (pleader, advocate, lawyer) in the nominative singular; see generally LSJ s.v.
[2] An exchange between the Informer and Peisetairos in Aristophanes, Birds 1423-1424 (web address 1) -- but here in reverse order: the 'happy craft' is informing (a.k.a. sycophancy: sigma 1330) rather than, as Suda readers might suppose, lawsuit-probing.