Keep it in reserve for formal ceremonies (5)

I believe the answer is:

rites

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'formal ceremonies' is the definition.
(I've seen this in another clue)

I cannot understand how the rest of the clue works.

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(Other definitions for rites that I've seen before include "Customary observances, religious say" , "Prescribed religious ceremonies" , "Tires of religious ceremonies" , "Formal ceremonial procedures" , "formal procedure" .)

I've seen this clue in the Evening Standard.

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