King George welcoming a toast (5)
I believe the answer is:
goner
'toast' is the definition.
(I know that toast can be written as goner)
'king george welcoming a' is the wordplay.
'king george' becomes 'gr' (Georgius Rex).
'welcoming' means one lot of letters goes inside another (in sense of 'inviting in').
'a' becomes 'one'.
'gr' going around 'one' is 'GONER'.
(Other definitions for goner that I've seen before include "Someone beyond any hope of recovery" , "Article ruined" , "without prayer?" , "A has-been in distress" , "one with no life left" .)