The most common and most likely answer to this crossword clue is the 7 letter word GROMMET
G
R
O
M
M
E
T
More clues leading to the result GROMMET
- Protective ring German field marshal left out in posh car
- Ring to listen to one half of animated pair
- Surfing tyro got mermaid helplessly rolling about
- Metal ring Desert Fox left out in sports car
- Madame going through rubbish finds ring
- C-Cyclops pinched by crap fastener
- Monty’s opponent with large cast in great ring
- Ring the companion of an inventor, we hear?
- Washer womanbeset by rubbish
Buddy explains!

The straight part
We know that "fastener" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case fastener = grommet.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 GROMMET mean?
GROMMET 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.
- To insert a grommet into.
- To fasten using a grommet.
- To apply grommets.