Fly off the handle (4,3,4)
I think it could be either:
rant and rave
'fly off the handle' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for lose ones rag that I've seen before include "Become very angry" , "fly off the handle" , "See red" , "Snap" , "Get very annoyed" .)
'fly off the handle' is the definition.
(thesaurus)
This is the entire clue.