Girl lacking in educational qualifications, got upset and hit the roof (3,3)
I believe the answer is:
see red
'hit the roof' is the definition.
(both can mean to become very angry)
'girl lacking in educational qualifications got upset' is the wordplay.
'girl' becomes 'g'.
'lacking in' indicates named letters should be taken away.
'educational qualifications' becomes 'degrees' (I've seen this before).
'got upset' says the letters should be written in reverse (I've seen 'getting upset' mean this).
'degrees' with 'g' taken away is 'derees'.
'derees' reversed gives 'SEE RED'.
'and' is the link.
(Other definitions for see red that I've seen before include "Burst a blood vessel" , "Become enraged" , "Lose temper like enraged bull" , "Become angry like bull" , "Become angry as bull might" .)