Sticky plant caught on pupils not expected back (8)
I believe the answer is:
cleavers
'sticky plant' is the definition.
'cleavers' can be an answer for 'plant' (cleavers is a kind of plant). I'm not sure about the 'sticky' bit.
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for cleavers that I've seen before include "Chopper's" , "goosegrass" , "crackers!" , "Heavy tools to chop meat" , "Butchers' tools" .)