Academic rejected passes for dunces (7)
I believe the answer is:
'dunces' is the definition.
(both can mean stupid people)
'academic rejected passes' is the wordplay.
'academic' becomes 'don' (type of academic - especially at Oxbridge).
'rejected' shows that the letters should be reversed in order.
'passes' becomes 'dies'.
'don' reversed gives 'nod'.
'for' acts as a link.
(Another definition for noddies that I've seen is "More than one bird".)