The most common and most likely answer to this crossword clue is the 4 letter word WELD
I've seen this crossword clue in The Times
W
E
L
D
More clues leading to the result WELD
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The straight part
We know that "joint" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case joint = weld.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 WELD mean?
WELD noun- A herb (Reseda luteola) related to mignonette, growing in Europe, and to some extent in America, used to make a yellow dye.
- The yellow coloring matter or dye extracted from this plant.
- The joint made by welding.
- To join two materials (especially two metals) together by applying heat, pressure and filler, either separately or in any combination.
- To bind together inseparably; to unite closely or intimately.
- To wield.