Entrench oneself at the dining table (3,2)
I believe the answer is:
dig in
'entrench oneself' is the definition.
(I've seen this in another clue)
'at the dining table' is the wordplay.
I cannot really understand how this works, but
'at' could be 'in' (synonymous in some cases - eg at school, in school) and 'in' is found in the answer.
The remaining letters 'dig' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for dig in that I've seen before include "protect himself" , "prepare trench" , "Enjoy the food" , "Begin eating (informal)" , "Start eating (informal)" .)