Travelling space, NASA orbits source of ice water (7,3)
I believe the answer is:
caspian sea
'water' is the definition.
(I know that Caspian Sea is a water)
'travelling space nasa orbits source of ice' is the wordplay.
'travelling' is an anagram indicator.
'orbits' is an insertion indicator.
'source of' says to take the initial letters (the start - or source - of the word).
The first letter of 'ice' is 'i'.
'space'+'nasa'='spacenasa'
'spacenasa' with letters rearranged gives 'caspansea'.
'caspansea' going around 'i' is 'CASPIAN SEA'.
(Other definitions for caspian sea that I've seen before include "World's largest inland body of water, fed by the Volga River" , "World's largest lake" , "Largest salt lake in the world" , "There's lots of water here" , "large expanse of water" .)