Unexpected obstacle (4)
I believe the answer is:
snag
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">unexpected obstacle</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 snag that I've seen before include "Hitch, obstacle" , "Unexpected difficulty" , "Temporary hold-up" , "hurdle?" , "Slight problem" .)