Meaning 3 here
flap [flæp]
vb flaps, flapping, flapped
1. to move (wings or arms) up and down, esp in or as if in flying, or (of wings or arms) to move in this way
2. to move or cause to move noisily back and forth or up and down the curtains flapped in the breeze
3. (intr) Informal to become agitated or flustered; panic
Flapping is used to mean panicking (eg for soccer defenders) , although it's more common;y used to represent being flustered