The most common and most likely answer to this crossword clue is the 4 letter word FAKE
F
A
K
E
Buddy explains!
The straight part
We know that "Ersatz" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case ersatz = fake.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.
What does FAKE mean?
FAKE noun- Something which is not genuine, or is presented fraudulently.
- A trick; a swindle.
- A move meant to deceive an opposing player, used for gaining advantage for example when dribbling an opponent.
- To cheat; to swindle; to steal; to rob.
- To modify fraudulently, so as to make an object appear better or other than it really is
- To make a counterfeit, to counterfeit, to forge, to falsify.
- To make a false display of, to affect, to feign, to simulate.
- Not real; false, fraudulent.
- (of people) Insincere.
- One of the circles or windings of a cable or hawser, as it lies in a coil; a single turn or coil.
- To coil (a rope, line, or hawser), by winding alternately in opposite directions, in layers usually of zigzag or figure of eight form, to prevent twisting when running out.