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" .)