Prominent scientist, not a German mug (5)
I believe the answer is:
stein
'german mug' is the definition.
(I've seen this in another clue)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for stein that I've seen before include "Inset (anag.)" , "Gertrude __, avant-garde US author, d. 1946" , "Gertrude ---; US writer" , "German earthenware beer mug" , "German tankard" .)