The most common and most likely answer to this crossword clue is the 6 letter word ULLAGE
I've seen this crossword clue in The Guardian
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More clues leading to the result ULLAGE
Buddy explains!
The straight part
We know that "Sort of deficiency" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case sort of deficiency = ullage.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 ULLAGE mean?
ULLAGE noun- In a wine bottle, the empty space between the cork and the top of the wine.
- In a cask or barrel, the empty space, occupied by air, that is created by not completely filling the cask or barrel, or through spillage.
- The topping-up of such a barrel with fresh wine.
- In an industrial setting, the empty space in a tank, such as for fuel.
- To gauge the amount of empty space between the top of a cask and the level of liquid inside it.