Union Pacific terminus (5)
I believe the answer is:
'union pacific terminus' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for omaha that I've seen before include "American Indian" , "Nebraska city and code-named beach of D-Day landings" , "US 1944 D-Day landing beach" , "Cotton fabric used for curtains and upholstery" , "American town" .)