Ill at ease, having no more classes? (3,2,5)
I believe the answer is:
out of sorts
'ill at ease' is the definition.
'having no more classes?' is the wordplay.
'having no more' becomes 'outof'.
'classes?' becomes 'sorts' ('sort' can be a synonym of 'class').
'outof'+'sorts'='OUT OF SORTS'
(Other definitions for out of sorts that I've seen before include "Not well" , "Not feeling quite right" , "Lacking variety" , "Not feeling good" , "Irritable" .)