Writer in old Tenby for broadcast (4,6)

I believe the answer is:

enid blyton

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'writer' is the definition.
(I've seen this before)

'in old tenby for broadcast' is the wordplay.
'in old tenby' anagrams to 'ENID BLYTON'.
Though, I'm not clear how the anagram is indicated.

Can you help me to learn more?

(Other definitions for enid blyton that I've seen before include "Famous Five author" , "Writer of children's books, d. 1968" , "Noddy's creator" , "Children's author" .)

I've seen this clue in The Telegraph.

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