Old Attic/Ionic form of the accusative of klei/s (kappa 1755).
The entry is the second half of one in Photius (Lexicon kappa762 Theodoridis), where the primary lemma is the infinitive klh=isai (should be klhi=+sai).
For an example of the present headword in tragedy, see Euripides, Medea 661. Thucydides has none, of either klhi=+sai or klhi=+da, but Theodoridis (above) reasonably takes the gloss as a general one, exemplified by e.g. Thuc. 2.4.3 (e)/klh|se) and 4.8.7 (klh|/sein).