End of teaching assessment is harsh (7)
I believe the answer is:
grating
'harsh' is the definition.
(synonyms)
'end of teaching assessment' is the wordplay.
'end of' suggests the final letters.
'assessment' becomes 'rating' (rating is a kind of assessment).
The final letter of 'teaching' is 'g'.
'g'+'rating'='GRATING'
'is' acts as a link.
(Other definitions for grating that I've seen before include "Lattice" , "Frame of iron bars to block passage but allow air" , "Frame of bars supporting a fire" , "Unpleasantly harsh in sound" , "Ring tag (anag.)" .)