The most common and most likely answer to this crossword clue is the 4 letter word CESS
I've seen this crossword clue in The Guardian
C
E
S
S
More clues leading to the result CESS
Buddy explains!
The straight part
We know that "Irish tax" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case irish tax = cess.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 CESS mean?
CESS noun- An assessed tax, duty, or levy.
- Usually preceded by good or (more commonly) bad: luck or success.
- Bound; measure.
- To levy a cess.
- The area along either side of a railroad track which is kept at a lower level than the sleeper bottom, in order to provide drainage.
- A bog, in particular a peat bog.
- A piece of peat, or a turf, particularly when dried for use as fuel.
- To cease; to neglect.