Green’s Dictionary of Slang

(Aus.) a sum of money, esp. money won from a bookmaker.

1897		W.A. Sun. Times (Perth) 19 Dec. 8/3: She sent round after the race to know how much the horse had drawn for her. The answer was that ‘her “div.” was a shilling’.
1900		Bulletin (Sydney) 27 Oct. 24/1: Sydney shop-totes swindle was never more glaring than on Saturday. [...] Once in a way big divs. are heard of, but ’tis any odds that the manipulator himself is the only one then ‘on.’.
1919		E. Dyson ‘How Herman Won the Cross’ in ‘Hello, Soldier!’ 81: He’s out to do his div. in, / ’N’ don’t care if he don’t go home till daylight doth appear.