Keeping quiet, explosive Egham individual that usually raises voice (9)

I believe the answer is:

megaphone

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'keeping quiet explosive egham individual that usually raises voice' is the definition.
Although both the answer and definition are singular nouns, I don't understand how one could define the other.

'keeping quiet explosive egham individual' is the wordplay.
'keeping' indicates putting letters inside.
'quiet' becomes 'p' (music symbol for 'piano', ie soft or quiet).
'explosive' indicates anagramming the letters.
'individual' becomes 'one' (an individual is one person).
'egham' anagrammed gives 'megah'.
'p' going inside 'megah' is 'megaph'.
'megaph'+'one'='MEGAPHONE'

Can you help me to learn more?

(Other definitions for megaphone that I've seen before include "hearing aid" , "Funnel-shaped voice amplifier" , "One projects sound" , "Loudhailer" , "Voice-amplifying device" .)

I've seen this clue in The Telegraph.

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