Sneak attending class with hesitation (8)
I believe the answer is:
informer
'sneak' is the definition.
(I've seen this before)
'attending class with hesitation' is the wordplay.
'attending' becomes 'in' (I've seen this in other clues).
'class' becomes 'form' (synonyms).
'with' is a charade indicator (letters next to each other).
'hesitation' becomes 'er' (sound used when hesitating).
'in'+'form'+'er'='INFORMER'
(Other definitions for informer that I've seen before include "Criminal helping police" , "One aiding police" , "who may betray someone?" , "sneak" , "One snitching to police" .)