Aim to keep call private? Ensured it's so (9)

I believe the answer is:

encrypted

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'ensured it's so' is the definition.
I can't judge whether this defines the answer.

'aim to keep call private?' is the wordplay.
'aim' becomes 'end' (I've seen this before).
'to keep' is an insertion indicator.
'call' becomes 'cry' (synonyms).
'private?' becomes 'pte'.
'cry'+'pte'='crypte'
'end' enclosing 'crypte' is 'ENCRYPTED'.

Can you help me to learn more?

(Other definitions for encrypted that I've seen before include "Of words, coded or enciphered" , "Describes information in code" , "Converted into code" .)

I've seen this clue in The Independent.

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