22 across
Young
German
friend
of
23
(4)
Young German friend of 23 (4)
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The whole clue is the definition (& lit or double definition).
How the clue works
Young German gives you the German word for "young" straight off, and then friend of 23 works as a second definition — where 23 refers to the answer to 23 down (FREUD), whose famous colleague this was. Two completely independent routes to the same answer.