Artistic movement wasting time with this case (12)
I believe the answer is:
aestheticism
'artistic movement' is the definition.
(19th-century philosophy of art)
'wasting time with this case' is the wordplay.
'wasting' indicates an anagram (waste can mean to destroy).
'with' says to put letters next to each other.
'this'+'case'='thiscase'
'time' after 'thiscase' is 'thiscasetime'.
'thiscasetime' anagrammed gives 'AESTHETICISM'.
(Other definitions for aestheticism that I've seen before include "sensitivity to beauty" , "The cult of the beautiful" .)