Call at a base (4)

I believe the answer is:
safe
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">call at a base</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 safe that I've seen before include "Strong metal box to store valuables" , "Locked store for money etc" , "Out of harm's way" , "Free from harm" , "Harmless" .)