The most common and most likely answer to this crossword clue is the 7 letter word LATCHES
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The straight part
We know that "fasteners" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case fasteners = latches.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 LATCHES mean?
LATCHES verb- To close or lock as if with a latch.
- To catch; lay hold of.
- A fastening for a door that has a bar that fits into a notch or slot, and is lifted by a lever or string from either side.
- A flip-flop electronic circuit
- A latching.
- A crossbow.
- That which fastens or holds; a lace; a snare.
- A breastfeeding baby's connection to the breast.
- A lightweight lock to protect internal structures from being modified by multiple concurrent accesses.
- To smear; to anoint.