Green’s Dictionary of Slang

clothes-peg n.²

[rhy. sl.; note Franklyn, Dict. of Rhyming Slang (1960) claims this usage is erroneous]

an egg.

1937–84		Partridge DSUE.
1998–2002		G.D. Smith Cockney Rhy. Sl. 🌐 Clothes Peg: Egg.