Securely (6)
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">securely</span>' is the definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for firmly that I've seen before include "fast" , "Resolutely" , "Strongly" , "With resolute determination" .)
(Other definitions for safely that I've seen before include "In a manner not exposed to danger" , "In a secure manner" , "Without danger" , "In a risk-free manner" .)