Rhapsodize producing Mercury retrospective taking in all the states in America (4)
I believe the answer is:
gush
'rhapsodize' is the definition.
(thesaurus)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for gush that I've seen before include "Pour forth" , "Flood out - enthuse" , "Spout like oil-well" , "Flow unceasingly" , "Effuse" .)