The most common and most likely answer to this crossword clue is the 4 letter word LOSE
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More clues leading to the result LOSE
Buddy explains!

The straight part
We know that "come second" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case come second = lose.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 LOSE mean?
LOSE verb- To cause (something) to cease to be in one's possession or capability due to unfortunate or unknown circumstances, events or reasons.
- To wander from; to miss, so as not to be able to find; to go astray from.
- To fail to win (a game, competition, trial, etc).
- To be unable to follow or trace (somebody or something) any longer.
- To cause (somebody) to be unable to follow or trace one any longer.
- To cease exhibiting; to overcome (a behavior or emotion).
- To shed, remove, discard, or eliminate.
- Of a clock, to run slower than expected.
- (ditransitive) To cause (someone) the loss of something; to deprive of.
- To fail to catch with the mind or senses; to miss.
- To cause to part with; to deprive of.
- Fame, renown; praise.