Struggled for breath (6)
I believe the answer is:
gasped
'struggled for breath' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for gasped that I've seen before include "Took a sharp breath" , "Struggled for breath" , "Breathed noisily" , "'Panted, puffed (6)'" , "Drew in breath sharply, as in surprise" .)