Join the staggeringly silent service? (6)

I believe the answer is:

enlist

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'join the staggeringly silent service?' is the definition.
'enlist' can be an answer for 'join' (I've seen this in another clue). I am not sure about the 'the staggeringly silent service?' bit.

'silent service?' is the wordplay.
'service?' indicates anagramming the letters (I've seen 'serviced' mean this (to service can mean to repair)).
'silent' with letters rearranged gives 'ENLIST'.

Can you help me to learn more?

(Other definitions for enlist that I've seen before include "Draft" , "Engage" , "Listen (anag.)" , "Join up, sign on" , "Join the armed forces" .)

I've seen this clue in the Evening Standard.

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