Concealed difficulty (5)
I believe the answer is:
catch
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">concealed difficulty</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for catch that I've seen before include "Ensnare" , "Grab; trick; fastener" , "Understand" , "Seize; start burning" , "Seize hold of" .)