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

The straight part
We know that "issue" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case issue = seep.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 SEEP mean?
SEEP noun- A small spring, pool, or other spot where liquid from the ground (e.g. water, petroleum or tar) has oozed to the surface; a place of seeping.
- Moisture, liquid, gas, etc. that seeps out; a seepage.
- The seeping away of a liquid, etc.
- A seafloor vent.
- To ooze or pass slowly through pores or other small openings, and in overly small quantities; said of liquids, etc.
- To enter or penetrate slowly; to spread or diffuse.
- To diminish or wane away slowly.