Mischievous child, one wielding lasso? That’s not right (8)
I believe the answer is:
improper
'not right' is the definition.
Both the answer and definition are adjectives. Perhaps you can see a link between them that I can't see?
'mischievous child one wielding lasso?' is the wordplay.
'mischievous child' becomes 'imp' (imp can mean a misbehaving child).
'one wielding lasso?' becomes 'roper' (I can't justify this - if you can you should give a lot more credence to this answer).
'imp'+'roper'='IMPROPER'
'that's' acts as a link.
Can you help me to learn more?
(Other definitions for improper that I've seen before include "Not fitting" , "Not decent, unseemly" , "So it may appear a fraction" , "Not decorous or seemly" , "Indecent or unsuitable" .)