Cave where King George met German emperor (6)
I believe the answer is:
grotto
'cave' is the definition.
(I know that cave can be written as grotto)
'where king george met german emperor' is the wordplay.
'where' indicates anagramming the letters (I've seen this in other clues).
'king' becomes 'R' (abbreviation of Latin rex).
'george' becomes 'g'.
'met' means one lot of letters go next to another.
'german emperor' becomes 'otto' (I've seen this before).
'r'+'g'='rg'
'rg' anagrammed gives 'gr'.
'gr'+'otto'='GROTTO'
(Other definitions for grotto that I've seen before include "(Imitation) cave" , "Small picturesque cave" , "It's left on Dec 24 by Santa and his reindeer" , "In company (with); over length of" , "Attractive natural, or artificial, cave" .)