Chicago's ___ Planetarium (5)
I believe the answer is:
adler
'chicago's planetarium' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for adler that I've seen before include "Austrian psychologist, 1870-1937" , "Contemporary of Freud, and German for eagle" , "Larry - - , mouth-organist" , "US musician" , "Alfred _; Austrian psychiatrist" .)