Crossword Genius

Fish in Test dropping end of fly (5)

Ross

I believe the answer is:

trout

'fish' is the definition.
(I know that trout is a type of fish)

I can't explain the remainder of the clue.

(Other definitions for trout that I've seen before include "air" , "Unattractive old woman" , "Tickled fish?" , "Schubert Quintet?" , "unpleasant old woman" .)

I've seen this clue in The Independent.
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