Drunk, perhaps, I am investing billions in German beer (7)
I believe the answer is:
imbiber
'drunk perhaps' is the definition.
(drunk is a kind of imbiber)
'i am investing billions in german beer' is the wordplay.
'i am' becomes 'I'm' (contraction).
'investing' indicates putting letters inside (inserted letters are taken in or invested).
'billions' becomes 'b' (abbreviation).
'in german beer' becomes 'bier' (I can't explain this - if you can you should give a lot more credence to this answer).
'b' placed inside 'bier' is 'biber'.
'im'+'biber'='IMBIBER'
Can you help me to learn more?
(Other definitions for imbiber that I've seen before include "chap at the bar" , ""I like a drink"" , "Drinker" , "one who keeps tumbler in hand" , "Sponge < and soak" .)