The headword (a single word in the Greek) is presumably extracted from the quotation given, and is thus transmitted, twice over, as the accusative singular of a masculine noun para/topos (which one could translate as "by-way" or "side-channnel"); but see the next two notes.
[1] The same gloss is given by Lexicon Vindobonense s.v. para\ to/pon -- sic: i.e. a prepositional phrase. In his edition of Polybius, F.O. Hultsch (1833-1906) gave that phrase as the headword here too, surely rightly.
[2] Polybius fr. 191 (Büttner-Wobst, p. 539). The fragment's placement is uncertain. Indeed, the Lexicon Vindobonense (loc. cit.) attributed it to Synesius. And Roos (Studia Arrianea; p. 53, n. 201) once linked the fragment to Arrian, Anabasis 6.19, where Alexander's ships enter into and then drop anchor in a channel at the mouth of the Indus River, near Patala, ancient India (Barrington Atlas map 5 grid B1, present-day Thatta (Thatto) Pakistan). Alexander's ships became grounded there during the extreme low tide, a phenomenon of ocean coastal regions that would be generally unknown to sailors accustomed to the benign tidal fluctuations of the Mediterranean Sea. However, Roos does not include (as Adler notes) this passage amongst the Arrian fragments (Scripta Minora et Fragmenta).
In her critical apparatus, Adler notes that mss AM transmit o(rmi/santes (they having moored, brought to anchor), and ms. A gives a)pori/an (desperation).