Green’s Dictionary of Slang

tidy! excl.

[tidy adj. (2)]

a general excl. of agreement or admiration.

[UK]N. Griffiths Grits 84: A [...] drive me fist streyt into is fuckin feyce, smack on is fuckin nose, crunch, broken a reckon, a hope. Felt it squash, I did. Bam. Tidy.