Guinness for one presented by east German plant (7)

I believe the answer is:

alecost

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'plant' is the definition.
(alecost is a kind of plant)

'guinness for one presented by east german' is the wordplay.
'guinness for one' becomes 'ale' (guinness is a kind of ale).
'presented by east german' becomes 'cost' (I can't justify this - if you can you should give a lot more credence to this answer).
'ale'+'cost'='ALECOST'

Can you help me to learn more?

(Other definitions for alecost that I've seen before include "Herb" , "plant" , "used to provide flavouring for beer" .)

I've seen this clue in The Independent.

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