The most common and most likely answer to this crossword clue is the 2 plus 4 letter word OH DEAR
I've seen this crossword clue in Independent
O
H
D
E
A
R
More clues leading to the result OH DEAR
- Duck heard, weirdly – that’s a worry
- In audition, character does well
- Bother! A request to analyse substance may follow…
- Poem being recited needs attention, alas
- Poem about horse with alligator skin – I don’t think that works!
- Skin of ostrich expensive, alas
- Try to accept daughter going along with nothing I say
- My poem on the radio, listener
- Poem about husband’s hard-core outpouring of despair
- Love to try nibbling slice of duck
Buddy explains!

The straight part
We know that "shit" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case shit = oh dear.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.