Justifies low exam grades and answers (8)

I believe the answer is:

deserves

'justifies' is the definition.
(both can mean to warrant)

'low exam grades and answers' is the wordplay.
'low exam grades' becomes 'DE' (D and E are low academic grades).
'and' says to put letters next to each other.
'answers' becomes 'serves' (answer can mean to serve for a particular purpose).
'de'+'serves'='DESERVES'

(Another definition for deserves that I've seen is " warrants".)

I've seen this clue in The Telegraph.

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