Mandarin tests? I don't know answer! (7)
I believe the answer is:
satsuma
'mandarin' is the definition.
(satsuma is a kind of mandarin)
'tests? i don't know answer' is the wordplay.
'tests?' becomes 'sats' (exams taken in UK schools).
'i don't know' becomes 'um' (I can't explain this - if you can you should give a lot more credence to this answer).
'answer' becomes 'a' (abbreviation eg in Q and A).
'sats'+'um'+'a'='SATSUMA'
Can you help me to learn more?
(Other definitions for satsuma that I've seen before include "Citrus fruit; Jap. pottery" , "As a must (anag)" , "Loose-skinned tangerine" , "Loose-skinned fruit" , "that's segmented" .)