Small nail or pin (4)
I believe the answer is:
tack
<span class="explanation-format__ClueExplanation">I believe this is a double definition.<br/ ><br/ >'<span class="explanation-format__original">small nail</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >'<span class="explanation-format__original">pin</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ ></span>
(Other definitions for tack that I've seen before include "vulgar" , "(Of a sailing ship) alter course through the wind" , "Nail - direction (eg of boat)" , "Rubbishy things" , "Small nail; sail (boat) against the wind" .)