The most common and most likely answer to this crossword clue is the 12 letter word HAND-ME-DOWN
I've seen this crossword clue in The Times
H
A
N
D
-
M
E
-
D
O
W
N
Buddy explains!
The straight part
We know that "used kit" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case used kit = hand-me-down.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 HAND-ME-DOWN mean?
HAND-ME-DOWN noun- An item that is passed along for someone else to use; especially, a piece of clothing or other item which has been outgrown by an older sibling and passed down to a younger one.
- Used or second-hand, passed along by its prior user.