Cassandra's somewhat stuck-up habits - I miss episode (9)
I believe the answer is:
pessimist
'cassandra's' is the definition.
(thesaurus)
'somewhat stuck-up habits i miss episode' is the wordplay.
'stuck up' shows that the letters should be reversed in order.
'somewhat' says the answer is hidden in the clue.
'tsimissep' is hidden in the letters of 'habits i miss episode'.
'tsimissep' back-to-front is 'PESSIMIST'.
(Other definitions for pessimist that I've seen before include "One sees the glass as always being half-empty" , "Half-empty-glass person" , "one anticipating the worst" , "One expects the worst" , "The glass is always half-empty for this person" .)