English strait (6)
I believe the answer is:
solent
'english strait' is the definition.
(I know that Solent is a sound)
This is all the clue.
(Other definitions for solent that I've seen before include "Water to north of IOW" , "Channel north of the Isle of Wight" , "Strait north of Isle of Wight" , "Confine as a prisoner" , "sound" .)