Financial supporters replacing leader with East German socialist (6)

I believe the answer is:

engels

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'german socialist' is the definition.
(I've seen this before)

I cannot understand how the remainder of the clue works.

(Other definitions for engels that I've seen before include "Early socialist" , "Co-author of Karl Marx" , ". . . and his friend, Friedrich" , "German linked to Marx" , "German socialist" .)

I've seen this clue in The Guardian.

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