Scottish inlet (5)
I believe the answer is:
firth
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">scottish inlet</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for firth that I've seen before include "Narrow sea inlet in Scotland" , "Estuary" , "Arm of the sea - actor Colin" , "Scottish river mouth" , "Scottish sea-inlet" .)