The flier crashed into the back of the helter-skelter! (7)

I believe the answer is:

kestrel

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'the flier' is the definition.
(kestrel is a kind of birdanimal)

'crashed into the back of the helter-skelter' is the wordplay.
'skelter' anagrams to 'KESTREL'.
However, I'm not sure how this is indicated.

Can you help me to learn more?

(Other definitions for kestrel that I've seen before include "It takes mice" , "Falcon that hovers" , "High flier" , "High-flyer" , "Bird of prey" .)

I've seen this clue in the Evening Standard.

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