Plant a great number around university (5)
I believe the answer is:
lotus
'plant' is the definition.
(lotus is a flowering plant)
'a great number around university' is the wordplay.
'a great number' becomes 'lots' (lots of something).
'around' indicates putting letters inside.
'university' becomes 'u' (abbreviation for university).
'lots' placed around 'u' is 'LOTUS'.
(Other definitions for lotus that I've seen before include "Fruit of forgetfulness - water lily - car marque" , "A blooming" , "Plant promoting forgetfulness" , "Tropical water-lily" , "Mythological fruit - lily" .)