Alex — he is prepared to breathe out (6)
I believe the answer is:
exhale
'to breathe out' is the definition.
('exhale' can be a synonym of 'breathe out')
'alex he is prepared' is the wordplay.
'is prepared' is an anagram indicator.
'alex'+'he'='alexhe'
'alexhe' with letters rearranged gives 'EXHALE'.
(Other definitions for exhale that I've seen before include "Puff perhaps" , "Give out" , "Puff away" , "expire" , "Joint of chicken" .)