Show impatience with one in examination class (8)
I believe the answer is:
tutorial
'class' is the definition.
(I've seen this before)
'show impatience with one in examination' is the wordplay.
'show impatience' becomes 'tut' (I've seen this in another clue).
'with' means one lot of letters go next to another.
'one' becomes 'i' (Roman numeral).
'in' is an insertion indicator.
'examination' becomes 'oral' (oral is a kind of examination).
'i' going within 'oral' is 'orial'.
'tut'+'orial'='TUTORIAL'
(Other definitions for tutorial that I've seen before include "Seminar" , "Private lesson" , "University lesson" , "Session of intensive teaching to an individual or small group" , "University study period" .)