Quick breathing (5)
I believe the answer is:
alive
I believe this is a double definition.
'quick' is the first definition.
(I've seen this before)
'breathing' is the second definition.
(I've seen this in another clue)
(Other definitions for alive that I've seen before include "Still in use, not dead" , "Breathing, existing" , "Alert, active" , "Still with us" , "Animated and kicking" .)