A cryptic crossword clue.....

[galosh]

" mice and rats take food inside an opening ".........

  ?e?t?s      Thanks all you smart a...s for your helpful replies.....

[mxyzptlk]

Seems to me that after several posts, nobody knows the answer - and if they did that sort of attitude is not going to make them inclined to help.

[uphillgrind]

Perhaps the answer is meatus which is an opening. m is the mice eat is the food and us being the smart a...s rats who didn't help you.