A Slav embraced by Kaiser Bill (4)
I believe the answer is:
serb
'a slav' is the definition.
(I've seen this in another clue)
'embraced by kaiser bill' is the wordplay.
'embraced by' says the answer is hidden in the clue (surrounding letters embrace the answer).
'SERB' is hidden within 'kaiser bill'.
(Other definitions for serb that I've seen before include "Native of the Balkans" , "Someone from Belgrade?" , "One from Belgrade" , "Eg, native of Belgrade" , "A European national" .)