Pass with low exam grade -- fall from high standard? (6)
I believe the answer is:
elapse
'pass' is the definition.
(synonyms)
'with low exam grade fall from high standard?' is the wordplay.
'with' is a charade indicator (letters next to each other).
'low exam grade' becomes 'E' (low academic grade).
'fall from high standard?' becomes 'lapse' (a lapse is a fall from grace).
'e'+'lapse' is 'ELAPSE'.
(Other definitions for elapse that I've seen before include "'Pass by, as time (6)'" , "Glide by" , "Please (anag) -- pass away" , "Passing" , "pass in silence" .)