King retaining old soldier, one of the late queen's favourites? (5)
I believe the answer is:
corgi
'one of the late queen's favourites?' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
'king retaining old soldier' is the wordplay.
'king' becomes 'CR' (short for Carolus Rex, King Charles in Latin).
'retaining' means one lot of letters goes inside another (inserted letters are held or retained).
'old' becomes 'o' (abbreviation).
'soldier' becomes 'GI' (term for US soldier).
'cr' enclosing 'o' is 'cor'.
'cor'+'gi'='CORGI'
Can you help me to learn more?
(Other definitions for corgi that I've seen before include "pet in 9 [CARDIFF]?" , "Queen's dog?" , "found in the kennels" , "Dog popular with British royals" , "Dog of Welsh breed, royal favourite" .)