Discourage passing having taken exam (10)
I believe the answer is:
demoralise
'discourage' is the definition.
('discourage'->'demoralize' is in my internal thesaurus and 'ize'->'ise')
'passing having taken exam' is the wordplay.
'passing' becomes 'demise' (I've seen this before).
'having taken' indicates putting letters inside.
'exam' becomes 'oral' (oral exam is a kind of exam).
'demise' enclosing 'oral' is 'DEMORALISE'.
(Other definitions for demoralise that I've seen before include "Make downhearted" , "Cause to lose confidence" , "Cause to lose confidence/hope" , "Crush" , "Throw into confusion" .)