Treble (6)
I believe the answer is:
triple
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">treble</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I know that treble can be written as triple)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for triple that I've seen before include "Threefold, treble" , "Three times" , "make score sixty?" , "Increase threefold" , "Multiply by three" .)