Increased threefold (7)
I believe the answer is:
trebled
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">increased threefold</span>' is the definition.<br/ ><span class="explanation-format__explanation">('treble' can be a synonym of 'increase threefold')</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for trebled that I've seen before include "produced twice as much again" , "Multiplied by three" , "Increased threefold" .)