To be of use (5)
I believe the answer is:
avail
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">to be of use</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for avail that I've seen before include "Be of value to" , "Medal (informal)" , "Make use, take advantage" , "Be of service to" , "(Of no) use or benefit" .)