Small, narrow space (6)
I believe the answer is:
cranny
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">small narrow space</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for cranny that I've seen before include "Small rock fissure" , "confined space" , "Crevice as hiding place" , "Crevice, goes with nook" , "Small narrow opening" .)