Pass first of exams, then blunder (6)
I believe the answer is:
elapse
'pass' is the definition.
(I've seen this before)
'first of exams then blunder' is the wordplay.
'first of' says to take the initial letters.
'then' means one lot of letters go next to another.
'blunder' becomes 'lapse'.
The initial letter of 'exams' is 'e'.
'e'+'lapse'='ELAPSE'
(Other definitions for elapse that I've seen before include "Go by - pass away" , "(Of time) go by" , "Pass away - asleep (anag)" , "Pass or expire - please" , "run by" .)