Mountain on the Gulf of Salonika (4)
I believe the answer is:
ossa
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">mountain on the gulf of salonika</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 ossa that I've seen before include "Hard things" , "So as to become a Greek mountain" , "To pile Pelion upon - is to make even greater" , "Technical name for bones" , "So as to turn to bones" .)