Spectrum (7)
'spectrum' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for rainbow that I've seen before include "Polychromatic arc" , "weather feature" , "heavenly sight" , "'I can sing a - - ' (song)" , "Arc of colored light in the sky" .)
'spectrum' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for gamut that I've seen before include "Complete extent or range" , "Ambit" , "Entire range" , "Entire scope" , "Compass, scale" .)