Some Dunkel, a German beer (5)
I believe the answer is:
lager
'beer' is the definition.
(lager is a kind of beer)
'some dunkel a german' is the wordplay.
'some' indicates the answer is hidden within the clue (some of the parts of the word are used).
'LAGER' can be found hidden inside 'dunkel a german'.
(Other definitions for lager that I've seen before include "Light beer; sounds like camp" , "Effervescent beer" , "Continental beer" , "Drink - 5 down (anag)" , "A regal sort of drink" .)