Naturally sticky semi-rubber solution (3)
I believe the answer is:
bur
'solution' is the definition.
Although both the answer and definition are singular nouns, I can't see how they can define each other.
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for bur that I've seen before include "Seed-case" , "sticker" , "small drill" , "Clinging seed case" , "Prickly seed case" .)