Green’s Dictionary of Slang

clam v.

(UK Und.) to beg.

1893

P.H. Emerson Signor Lippo 54: So he started walking about clamming, getting a few medazas from one and another, fairly on the pross. [Ibid.] 83: I get plenty of mungarley [...] and I give a lot away to any needy who’s clamming.

In phrases