Green’s Dictionary of Slang

gnaw v.

(N.Z.) to kiss.

1988		McGill Dict. of Kiwi Sl. 50/2: gnawing kissing, streetkid style; eg ‘We did some gnawing, that was it. She didn’t want to go any further.’.
2003		McGill Reed Dict. of N.Z. Sl. [as cit. 1988].

SE in slang uses

In phrases