Crossword Genius

What’s sticky and hard to throw away? (9)

Ross

I believe the answer is:

boomerang

I'm a little stuck... Click here to teach me more about this clue!

'throw away?' is the definition.
The definition and answer can be both acts as well as being singular nouns.
Perhaps they are linked in a way I don't understand?

I don't understand the remainder of the clue.

Can you help me to learn more?

(Other definitions for boomerang that I've seen before include "Primitive weapon" , "Aboriginal projectile" , "Self-returning missile" , "Curved throwing stick" , "Recoil from" .)

I've seen this clue in The Times.
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