Meaning: something very small, short, or young. Use examples. Origins.
Rewrite 1: knee-high to a cricket
Rewrite 2: no taller than a gnome’s knees
Rewrite 3: no higher than putting green grass
Rewrite 4: no bigger than a barrel full of fleas
Rewrite 5: he’d grown no bigger than a chipmunk’s left thumb

Comment: I’ve always wanted to use rewrite 2, it’s so vivid.

More reading about clichés
What I found when I googled “clichés”:
• Clichés Exercise: “To illustrate how dull and predictable clichés are, see how easy it is to fill in the missing words in the last half of the examples below.”