King George imitates fruit (6)
I believe the answer is:
grapes
'fruit' is the definition.
(grapes are fruit)
'king george imitates' is the wordplay.
'king george' becomes 'gr' (Georgius Rex).
'imitates' becomes 'apes' ('ape' can be a synonym of 'imitate').
'gr'+'apes'='GRAPES'
(Other definitions for grapes that I've seen before include "Vine fruits" , "Fruit for wine" , "John Steinbeck wrote 'The . . . . . . of Wrath'" , "See 10 Across" , "'Green, black or purple clusters (6)'" .)