Green’s Dictionary of Slang

1. (orig. Aus.) to act in a given manner, defined by some form of comb., e.g. crack hardy

1972		G.W. Turner Eng. Lang. in Aus. and N.Z. 108: An Adelaide student reported [...] in 1968 that in April of that year her brother on a trip to Sydney found that the fashionable slang word was then crack. You would crack a greenie ‘go surfing’, crack a coldie ‘open a bottle of beer’.
1979		Lette & Carey Puberty Blues 51: ‘What happened?’ ‘He cracked a mental.’.

2. (Aus.) to pretend, to sham; thus crack a deaf ’un, to pretend to be deaf, or not to hear.

1900		Sydney Sportsman (Surry Hills, NSW) 10 Oct. 1/1: For years past I’ve been trying to unearth a self-admitted cronk ’un, but they will all persist in cracking dead squares.
1902		Bulletin (Sydney) 15 Nov. 31/2: But I tell yer times is getting so hard that I has ter crack deaf and write it on paper when I arsks for chuck; an’ sometimes I forgets myself. That’s ’ow I ’eard what you said.
1911		E. Dyson ‘The Big Spoof’ in Benno and Some of the Push 215: Little Benno, lyin’ low, crackin’ soft silly, does the ’gun fer all he owns, gets home with the boodle.
2016		D. Whish-Wilson Old Scores [ebook] Riley talked like a mug, but that was just him cracking dumb.

3. (US black) to happen.

2002

‘Touré’ Portable Promised Land (ms.) 160: We Words (My Favorite Things) [...] It’s crackin. What’s poppin? What’s hapnin? What’s cracka-lackin? Whatever’s clever.