Give a false alarm (3,4)
I believe the answer is:
cry wolf
'give a false alarm' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for cry wolf that I've seen before include "Cause a false alarm" , "alarm unnecessarily" , "Give unnecessary cause for alarm" , "Raise a false alarm too often, then not being believed when help is really needed" , "Give false alarm" .)