Game left by German emperor (5)
I believe the answer is:
lotto
'game' is the definition.
(the UK National Lottery)
'left by german emperor' is the wordplay.
'left by' becomes 'l' (I've seen this in other clues).
'german emperor' becomes 'otto' (I've seen this in another clue).
'l'+'otto'='LOTTO'
(Other definitions for lotto that I've seen before include "Venetian painter - gambling game" , "Game like bingo" , "Children's game; lottery" , "Housey-housey, bingo" , "chancy business" .)