In another form, it's not very good (6,5)
I believe the answer is:
second class
'not very good' is the definition.
The answer and definition can be both human attributes as well as being singular nouns.
Perhaps there's an association between them I don't understand?
'in another form' is the wordplay.
'in another' becomes 'second' (I am not sure about the 'in' bit.).
'form' becomes 'class' (synonyms).
'second'+'class'='SECOND-CLASS'
'it's' acts as a link.
Can you help me to learn more?
(Other definitions for second class that I've seen before include "Of inferior status" , "Next-to-best quality" , "mediocre" , "Not of the top group" , "Next to best" .)