Love one part of school that's stupid (6)
I believe the answer is:
oafish
'stupid' is the definition.
(I've seen this in another clue)
'love one part of school' is the wordplay.
'love' becomes 'o' (love means zero in tennis).
'one part of school' becomes 'afish' (I can't explain this - if you can you should give a lot more credence to this answer).
'o'+'afish'='OAFISH'
'that's' is the link.
Can you help me to learn more?
(Other definitions for oafish that I've seen before include "Like a boorish person" , "Doltish" , "Bone-headed" , "Boorish, clumsy" , "Stupid, boorish" .)