One suffering for their beliefs (6)
I believe the answer is:
martyr
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">one suffering for their beliefs</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for martyr that I've seen before include "One who suffers for beliefs" , "One suffers for the sake of principle" , "put at stake?" , "One suffering or dying for a cause" , "One killed for cause" .)