OK Computer overshadowed by a second big hit when making a comeback (8)

I believe the answer is:
oklahoma
'ok' is the definition.
(I've seen this before)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for oklahoma that I've seen before include "American state and famous musical" , "S. central US state" , "A holm oak found over in the States" , "American state and great western musical" , "State between Kansas and Texas" .)
