Breathe in/out and have a long sleep (9)
I believe the answer is:
hibernate
'have a long sleep' is the definition.
(to hibernate is to sleep through the winter)
'breathe inout and' is the wordplay.
I cannot really understand how this works, but
'breathe' could be 'be' (breathe can mean to be or exist) and 'be' is present in the answer.
'and' could be 'n' (common abbreviation for 'and') and 'n' is found in the answer.
This explanation may well be incorrect...
(Other definitions for hibernate that I've seen before include "Of animals, sleep through the winter" , "Sleep durning winter" , "Become dormant" , "Pass the winter in a dormant state" , "Breathe in for long winter sleep" .)