Forbidden style for a boot (5)

I believe the answer is:

taboo

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

'forbidden' is the definition.
(synonyms)

'style for a boot' is the wordplay.
'a boot' anagrams to 'TABOO'.
Though, I am not clear how the anagram is indicated.

Can you help me to learn more?

(Other definitions for taboo that I've seen before include "A ban or prohibition of superstitious kind" , "Prohibited; ban" , "By religion or custom, not to be done or touched" , "Ritual prohibition" , "Inhibition based on social custom" .)

I've seen this clue in the Evening Standard.

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