Some Cryptic Clues
19a...Just after having mastered the subject(4)...??O?
23a...Former pupils with papers return excellent new glass(8)...O???????
26a...Suspicious heading off around, leave everywhere at once(10)...U?I???????
28a...Premonition about way for early immigrants(6)...??????
2d...Initially large area can be easily excitable(5)...L?T?N
16d...Acted up to violent political turmoil(4,5)...C??? ?????
20d...By the way, European party is not what it thinks it is(6)...??????
24d...Literary leaders employ blackguard(5)...?????