Legal action about university grounds (5)
I believe the answer is:
cause
'grounds' is the definition.
(I've seen this in another clue)
'legal action about university' is the wordplay.
'legal action' becomes 'case' (a legal case).
'about' is an insertion indicator.
'university' becomes 'u' (abbreviation for university).
'case' going around 'u' is 'CAUSE'.
(Other definitions for cause that I've seen before include "Grounds" , "Reason; belief" , "Make happen; something deserving support" , "Bring about" , "Genesis" .)