Additional payment (5)
I believe the answer is:
bonus
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">additional payment</span>' is the definition.<br/ ><span class="explanation-format__explanation">(payment added to one's salary)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for bonus that I've seen before include "Something more than you expected" , "- generis means unique" , "Additional wage" , "The advantage" , "Extra money paid for good performance" .)