Croaky on the radio and on local television in the trailer for Black Beauty, presumably (8)

I believe the answer is:

horsebox

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But I can't explain it at all! Could you help me understand?

(Other definitions for horsebox that I've seen before include "road trailer" , "It takes animals to the races" , "Equine conveyance" , "Equine transporter" , "Animal transporter" .)

I've seen this clue in The Irish Times.

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