Oddly silent coves (6)
I believe the answer is:
inlets
'coves' is the definition.
('inlet' can be a synonym of 'cove')
'oddly silent' is the wordplay.
'oddly' is an anagram indicator.
'silent' is an anagram of 'INLETS'.
(Other definitions for inlets that I've seen before include "Small bays of silent kind" , "Silent as sea entries to land" , "Narrow channels of water running from sea or river" , "Small arms off larger bodies of water" , "Silent strips of water" .)