Be constantly anxious (4)
I believe the answer is:
fret
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">be constantly anxious</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 fret that I've seen before include "Sort of saw work" , "Worry unnecessarily" , "ridge > that obscures sea view" , "Mist coming in from the sea" , "Worry - decoration - part of guitar" .)