Peaceful waters? (7)
I believe the answer is:
pacific
This clue might be a double definition.
'peaceful' is the first definition.
(similar in meaning)
'waters?' is the second definition.
Although both the answer and definition are singular nouns, I cannot see how one could define the other.
Can you help me to learn more?
(Other definitions for pacific that I've seen before include "Serene - ocean" , "water" , "See 18" , "A great ocean" , "Large ocean" .)