Keeping quiet when having doubt (12)

I believe the answer is:

preservation

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

'quiet when having doubt' is the wordplay.
'quiet' becomes 'p' (music symbol for 'piano').
'when having' is a charade indicator (letters next to each other).
'doubt' becomes 'reservation' (reservation is a kind of doubt).
'p'+'reservation'='PRESERVATION'

(Another definition for preservation that I've seen is " Keeping".)

I've seen this clue in The Telegraph.

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