The most common and most likely answer to this crossword clue is the 4 letter word LACK
L
A
C
K
More clues leading to the result LACK
- Filthy topless miss
- Want some special acknowledgement
- Want to take it easy when head’s away
- Want chess player to sacrifice bishop
- Deficiency in chess player losing first piece
- Want servant to get the old west-facing shed
- Want a great sum in India to kickstart
- Absence of chess player, missing start
- Need jet after takeoff?
- Deficiency of chessplayer losing bishop
Buddy explains!

The straight part
We know that "Deficiency" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case deficiency = lack.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 LACK mean?
LACK noun- A defect or failing; moral or spiritual degeneracy.
- A deficiency or need (of something desirable or necessary); an absence, want.
- To be without, to need, to require.
- To be short (of or for something).
- To be in want.
- To see the deficiency in (someone or something); to find fault with, to malign, reproach.