The most common and most likely answer to this crossword clue is the 5 letter word GROAT
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More clues leading to the result GROAT
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The straight part
We know that "Old-style fourpenny one’s" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case old-style fourpenny one’s = groat.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 GROAT mean?
GROAT noun- (chiefly in the plural) Hulled grain.
- Any of various old coins of England and Scotland.
- A historical English silver coin worth four English pennies, still minted as one of the set of Maundy coins.
- A proverbial small sum; a whit or jot.