Wave in panic (4)
I believe the answer is:
flap
This clue is a double definition.
'wave' is the first definition.
(flap is a kind of wave)
'panic' is the second definition.
(thesaurus)
'in' acts as a link.
(Other definitions for flap that I've seen before include "Minor panic; tab" , "Tab - tizzy - move wings" , "Agitated state; tab" , "Use wings; be agitated" , "Be agitated; hinged piece" .)