Run out of breath (6)
I believe the answer is:
expire
'run' is the definition.
(thesaurus)
'out of breath?' is the wordplay.
'out of' becomes 'ex' ('out of' in Latin).
'breath?' becomes 'pire' (I can't justify this - if you can you should believe this answer much more).
'ex'+'pire'='EXPIRE'
Can you help me to learn more?
(Other definitions for expire that I've seen before include "Die or terminate" , "Die, give out" , "Lose validity" , "Come to an end; die" , "Die or go out of date" .)