Meaning: extremely weak. Use examples.
Rewrite 1: you could have knocked me over with a leaf
Rewrite 2: so beat, a feather could have knocked me out
Rewrite 3: such a wuss I was afraid a dandelion seed would push me over
Rewrite 4: so weak, I couldn’t stand straight on a windless day
Comment: This is really a metaphor about weakness, whether it’s physical or mental.

More reading about clichés
What I found when I googled “clichés”:
• Web Design Tips, “The purpose of this web site is to help out new web developers by going over some of the tips of how to put together a top-quality, professional web site.”