Grandmother entering university with one tailless rodent is in complete agreement (9)
I believe the answer is:
unanimous
'in complete agreement' is the definition.
(I've seen this before)
'grandmother entering university with one tailless rodent is' is the wordplay.
'grandmother' becomes 'nan' (nan can informally mean a grandmother).
'entering' is an insertion indicator.
'university' becomes 'u' (abbreviation for university).
'with' is an insertion indicator.
'one tailless rodent' becomes 'mou' (I can't explain this - if you can you should believe this answer much more).
'mou' placed into 'is' is 'imous'.
'u'+'imous'='uimous'
'nan' inserted within 'uimous' is 'UNANIMOUS'.
Can you help me to learn more?
(Other definitions for unanimous that I've seen before include "All in agreement, no exceptions" , "Agreed by all, nem con" , "no-one disagreeing" , "With one mind" , "Concerted" .)