Obviously not the best group to teach (6,5)
I believe the answer is:
second class
'obviously' is the definition.
Both the definition and answer are adverbs. Perhaps you can see a link between them that I don't see?
'not the best group to teach' is the wordplay.
I cannot quite understand how this works, but
'not' could be 'con' (I've seen this in other clues) and 'con' is present in the answer.
'best' could be 'a' and 'a' is found within the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for second class that I've seen before include "Next to best" , "not making the top grade" , "mediocre" , "B-rated" , "Less than first rate" .)