Whence regally to send a friend a card? (6)

I believe the answer is:

palace

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'whence regally to send a' is the definition.
I can't judge whether this definition defines the answer.

'friend a card?' is the wordplay.
'friend' becomes 'pal' (pal can mean a friend).
'a card?' becomes 'ace' (ace is a type of playing card).
'pal'+'ace'='PALACE'

Can you help me to learn more?

(Other definitions for palace that I've seen before include "Large building" , "See 16" , "Head of state's residence" , "Castle" , "Royal dwelling" .)

I've seen this clue in the Evening Standard.

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