Crossword Genius

Is it to be sniffed at? (5)

Ross

I believe the answer is:

smell

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

'at?' is the definition.
Although both the answer and definition are singular nouns, I cannot see how one could define the other.

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for smell that I've seen before include "Sniff" , "stink" , "Scent" , "Aroma" , "Unpleasant odour" .)

Want a hint initially instead of a full solution? Install my app