Nothing other than; perpendicular (5)
I believe the answer is:
sheer
<span class="explanation-format__ClueExplanation">This clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">nothing other than</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >'<span class="explanation-format__original">perpendicular</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ ></span>
(Other definitions for sheer that I've seen before include "Gossamer or precipitous" , "Downright - deviation" , "Absolutely - diaphanous" , "Unmitigated; perpendicular" , "Very thin and fine" .)