Period charm (5)

I believe the answer is:

spell

I believe this clue is a double definition.

'period' is the first definition.
(spell is a kind of period)

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

(Other definitions for spell that I've seen before include "JP" , "get letters in order" , "Indicate" , "Identify individual characters" , "Short period of time; incantation" .)

I've seen this clue in The Independent, The Telegraph, The Times and The Guardian.

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