Bump one's head and lose one's rag (3,3,7)
I believe the answer is:
hit the ceiling
'lose one's rag' is the definition.
I can't tell whether this defines the answer.
'bump one's head' is the wordplay.
'bump' becomes 'hit' (synonyms).
'one' becomes 'the' (both can introduce a definite example of something).
'head' becomes 'ceiling' (I am not sure about this - if you are sure you should believe this answer much more).
'hit'+'the'+'ceiling'='HIT THE CEILING'
'and' acts as a link.
Can you help me to learn more?
(Other definitions for hit the ceiling that I've seen before include "Overzealous pogo dancer might" , "combust" .)