The most common and most likely answer to this crossword clue is the 7 letter word PARLAYS
I've seen this crossword clue in The Guardian
P
A
R
L
A
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S
Buddy explains!
The straight part
We know that "bets using previous winnings" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case bets using previous winnings = parlays.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 PARLAYS mean?
PARLAYS noun- (originally United States) A bet or series of bets where the stake and winnings are cumulatively carried forward; an accumulator.
- To carry forward the stake and winnings from a bet on to a subsequent wager or series of wagers.
- (by extension) To increase (an asset, money, etc.) by gambling or investing in a daring manner.
- (by extension, generally) To convert (a situation, thing, etc.) into something better.
- To have a discussion, especially one between enemies.