Science degree thus not needing university (5)
I believe the answer is:
maths
'science' is the definition.
(maths is a kind of science)
'degree thus not needing university' is the wordplay.
'degree' becomes 'ma' (Master of Arts is a type of degree**).
'not needing' indicates named letters should be taken away.
'university' becomes 'u'.
'thus' with 'u' taken out is 'ths'.
'ma'+'ths'='MATHS'
(Other definitions for maths that I've seen before include "Study of numbers and sums" , "The science of number, quantity and space" , "A school subject (abbr.)" , "Science dealing with quantity and shapes, in short" , "Algebra, geometry, calculus etc (abbr)" .)