Cancel new university students (4)
I believe the answer is:
null
'cancel' is the definition.
The definition and answer are not the same part of speech.
'new university students' is the wordplay.
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'university' becomes 'U' (abbreviation for university).
'students' becomes 'LL' (two abbreviations for learner).
'n'+'u'+'ll'='NULL'
Can you help me to learn more?
(Other definitions for null that I've seen before include "... and void, lacking any legal or binding force" , "Useless - nothing" , "Without legal force" , "Non-existent and void" , "Amounting to nothing" .)