The most common and most likely answer to this crossword clue is the 8 letter word GROMMETS
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Buddy explains!
The straight part
We know that "reinforcements" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case reinforcements = grommets.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 GROMMETS mean?
GROMMETS noun- A reinforced eyelet, or a small metal or plastic ring used to reinforce an eyelet.
- A ring formed of a single strand of rope, laid in three times round, fastening the upper edge of a sail to its stay.
- (flags) An eyelet at the hoist end of a flag, used to fasten the flag to its halyard.
- A young or inexperienced surfer, skateboarder or snowboarder.
- A boy serving on a ship.