Travels after poor exam grades for mocks (7)
I believe the answer is:
derides
'mocks' is the definition.
(deriding is a kind of mocking)
'travels after poor exam grades' is the wordplay.
'travels' becomes 'rides' (riding is a kind of traveling**).
'after' says to put letters next to each other.
'poor exam grades' becomes 'de' (D and E are poor exam grades).
'rides' put after 'de' is 'DERIDES'.
'for' acts as a link.
(Other definitions for derides that I've seen before include "Mocks, scorns" , "Ridicules" , "Laughs at" .)