Indifferent nature affected student (7)
I believe the answer is:
neutral
'indifferent' is the definition.
('neutral' can be a synonym of 'indifferent')
'nature affected student' is the wordplay.
'affected' indicates anagramming the letters.
'student' becomes 'l' (as in L-plates for learner drivers).
'nature' anagrammed gives 'neutra'.
'neutra'+'l'='NEUTRAL'
(Other definitions for neutral that I've seen before include "Grey" , "Inoffensive; beige colour" , "negative or positive? Neither" , "A runlet? (anag)" , "'Impartial, unbiased (7)'" .)