Not loose (5)
I believe the answer is:
tight
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">not loose</span>' is the definition.<br/ ><span class="explanation-format__explanation">('tight' is the opposite to 'loose')</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for tight that I've seen before include "Penny-pinching" , "Steaming" , "Bottled ," , "Close-fitting; drunk" , "Drunk; giving little room" .)