An older man respected for his expertise on the youth culture
of the 1950s and early 1960s.

From the French, eminence grise, or "gray eminence, an
influential advisor or mentor.
For younger folks, Dick Clark is something of an eminence grease, given his encyclopedic knowledge of classic 1950s rock n' roll.
by I.M.Salmon May 1, 2010
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