Crossword Genius

Fish devouring fantastic bat -- suspect treachery? (5,1,3)

Ross

I believe the answer is:

smell a rat

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

'suspect treachery?' is the definition.
'smell a rat' can be an answer for 'suspect' (to smell a rat is to suspect something). I am not sure about the 'treachery?' bit.

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for smell a rat that I've seen before include "Suspect something wrong" , "Have suspicion something is afoot" , "Find something fishy" , "Sense something suspicious" , "Suspect deception" .)

I've seen this clue in The Telegraph.
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