Messy university cleared out pens books and papers (6)
I believe the answer is:
untidy
'messy' is the definition.
(synonyms)
'university cleared out pens books and papers' is the wordplay.
'cleared out' suggests removing the centre.
'pens' is an insertion indicator (inserted letters are held or penned in).
'books' becomes 'NT' (New Testament).
'and' is a charade indicator (letters next to each other).
'papers' becomes 'ID' (short for identification papers).
'university' with its centre removed is 'uy'.
'nt'+'id'='ntid'
'uy' placed around 'ntid' is 'UNTIDY'.
(Other definitions for untidy that I've seen before include "Cluttered" , "Higgledy-piggledy" , "Disorderly, messy" , "Disordered" , "Messy, not neat" .)