Entrench oneself (3,2)
I believe the answer is:
dig in
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">entrench oneself</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 dig in that I've seen before include "Begin eating heartily" , "Start to scoff" , "prepare trench" , "protect himself" , "Start eating (informal)" .)