The most common and most likely answer to this crossword clue is the 3 plus 3 plus 6 letter word RIP VAN WINKLE
I've seen this crossword clue in The Guardian
R
I
P
V
A
N
W
I
N
K
L
E
More clues leading to the result RIP VAN WINKLE
- VIP ran to exchange starters with shellfish for famed kipper
- Kipper in front, farewell forever seafood sandwiches!
- Rent vehicle plant that was dormant for a long period
- Somnolent type to tear open vehicle with seafood
- He stayed out for ages — considered late upon returning
- Character associated with ‘The Big Sleep’? Yes and no
Buddy explains!
The straight part
We know that "that was dormant for a long period/that was dormant for a long period" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case that was dormant for a long period/that was dormant for a long period = rip van winkle.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.