Designed to prevent accidents by obstructing contrary pupils' nonsense (7)
I believe the answer is:
nonslip
'designed' is the definition.
Both the definition and answer are adjectives. Perhaps you can see a link between them that I can't see?
'prevent accidents by obstructing contrary pupils' nonsense' is the wordplay.
'NONSLIP' is hidden backwards in amongst the letters.
However, I'm not sure how this is indicated.
'to' is the link.
Can you help me to learn more?
(Other definitions for nonslip that I've seen before include "Designed for secure footing" , "Preventing sliding" , "(Of surface) affording a strong grip" , "unlikely to slide" , "Designed not to slide unexpectedly" .)