The most common and most likely answer to this crossword clue is the 6 letter word BOBBIN
I've seen this crossword clue in The Guardian
B
O
B
B
I
N
Buddy explains!

The straight part
We know that "a reel" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case a reel = bobbin.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 BOBBIN mean?
BOBBIN noun- A spool or cylinder around which wire is coiled.
- In a sewing machine, the small spool that holds the lower thread.
- The little rounded piece of wood at the end of a latch string, which is pulled to raise the latch.
- (haberdashery) A fine cord or narrow braid.