The most common and most likely answer to this crossword clue is the 6 letter word SHMUCK
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Buddy explains!
The straight part
We know that "an unlikeable person" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case an unlikeable person = shmuck.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 SHMUCK mean?
SHMUCK noun- A jerk; a person who is unlikable, detestable, or contemptible because he or she is stupid, foolish, clumsy, oafish, inept, malicious, or unpleasant.
- A deplorable, pitiful person; often in the form poor schmuck.