Sound Holden filling in work day (5)
I believe the answer is:
fjord
'sound' is the definition.
(thesaurus)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for fjord that I've seen before include "Northern location?" , "Sea inlet" , "part of Norway" , "Rock-bound inlet" , "Norwegian inlet (J, not I)" .)