Guardedness about nest-egg? (7)

I believe the answer is:

reserve

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'guardedness' is the definition.
(thesaurus)

'about nest-egg?' is the wordplay.
'about' becomes 're' ('re' means regarding or about).
'nest-egg?' becomes 'serve' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
're'+'serve'='RESERVE'

Can you help me to learn more?

(Other definitions for reserve that I've seen before include "Keep for future use" , "Bank" , "cool" , "Order" , "Hold back" .)

I've seen this clue in The Irish Independent.

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