Catch one's breath (4)
I believe the answer is:
gasp
'catch one's breath' is the definition.
(to gasp is to pant)
This is the entire clue.
(Other definitions for gasp that I've seen before include "Pant" , "Gaps in struggle for breath" , "Breathe sharply in amazement, horror etc" , "Sound of astonishment" , "Catch one's breath in astonishment" .)