Green’s Dictionary of Slang

crackling n.

[SE crackling, tasty roast pork fat]

attractive women, used as a generic.

[UK]A. Fowles Dupe Negative 73: She was no lady. [...] Sir Bernard, in his rags to riches climb, must have retained a preference for crackling [OED].
[UK]Partridge DSUE (8th edn) 264/2: since ca. 1890.
[UK]J. Morton Lowspeak.

In phrases

bit of crackling (n.) [bit n.1 (2a)]

1. an attractive woman.

E.W. Rogers [perf. Marie Lloyd] The Barmaid [lyrics] ‘Ror-ty bit o’ crackling don’t you think so?’.
[UK]‘Doss Chiderdoss’ ‘A Courting Case in Court’ Sporting Times 7 Apr. 1/4: When you go about, / After work, with your own bit of crackling, / How would you like to have some long fat-headed slop, / When a kiss from your gal you’re extorting, / Come along and inform you that you he will cop / For assault, when you’re only a-courting?
posting at [Internet] You Cheeky personage......Although I’ve been called ‘a lovely bit of crackling’.

2. an attractive man.

[UK]E. Pugh Cockney At Home 138: I’ll kindly request you to keep your gooseberry optics off my bit o’ cracklin’, if you don’t mind. Go an’ find someone your own age, you low female!