Nobel Prize physicist from Germany (6)
I believe the answer is:
planck
'nobel prize physicist from germany' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for planck that I've seen before include "German physicist giving name to a constant" , "Max ---, quantum theorist" , "German physicist, initiator of quantum theory, d. 1947" , "Max --, German scientist, gave name to a constant" .)