Eldest of the Three Musketeers (5)
I believe the answer is:
athos
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">eldest of the three musketeers</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for athos that I've seen before include "Brave soldier" , "Literary musketeer" , "Dumas musketeer" , "Greek mount; one of the Three Musketeers" , "Mount - musketeer" .)