Like the open sea (4)
I believe the answer is:
vast
(Other definitions for vast that I've seen before include "'Huge, immense (4)'" , "Colossal" , "Boundless" , "Astronomical" , "Unusually great" .)
I believe the answer is:
vast
(Other definitions for vast that I've seen before include "'Huge, immense (4)'" , "Colossal" , "Boundless" , "Astronomical" , "Unusually great" .)