The most common and most likely answer to this crossword clue is the 6 plus 5 letter word SPIRIT LEVEL
I've seen this crossword clue in The Daily Telegraph
S
P
I
R
I
T
L
E
V
E
L
More clues leading to the result SPIRIT LEVEL
- Soul even, in tool
- Brickie could use this degree of enthusiasm
- Device showing if someone’s been at the gin?
- What surveyor may use in flat after ghost is seen
- What a builder might use to maintain equanimity?
- What told builder if someone had been at his whisky?
- Handyman should have his enthusiasm well-balanced
- Flat-finding agency
Buddy explains!
The straight part
We know that "Device" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case device = spirit level.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.