Test the breath of a flier (4)

I believe the answer is:

moth

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

'a flier' is the definition.
(something which flies)

'test the breath' is the wordplay.
'test' becomes 'MOT' (as in an MOT test for a vehicle).
'the breath' becomes 'h' (I am not sure about this - if you are sure you should believe this answer much more).
'mot'+'h'='MOTH'

'of' acts as a link.

Can you help me to learn more?

(Other definitions for moth that I've seen before include "Insect, mainly nocturnal" , "Shakespearean fairy?" , "Night-flier" , "Insect; MND fairy" , "Insect of the order lepidoptera" .)

I've seen this clue in the Evening Standard.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.