The most common and most likely answer to this crossword clue is the 4 letter word BEST
I've seen this crossword clue in The Guardian
B
E
S
T
More clues leading to the result BEST
Buddy explains!
The straight part
We know that "Worst as one part of speech/only one" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case worst as one part of speech/only one = best.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 BEST mean?
BEST noun- The supreme effort one can make, or has made.
- One's best behavior.
- The person (or persons; or thing or things) that is (are) most excellent.
- To surpass in skill or achievement.
- To beat in a contest
- Most; largest.
- Most superior; most favorable.
- (of people)
- (of capabilities)
- (properties and qualities)
- (when with and) Very, extremely. See good and.
- Holy (especially when capitalized) .
- (of quantities)
- (manner) Accurately, competently, satisfactorily.
- (manner) Completely, fully.
- (degree) To a significant degree.
- (degree) Very (as a general-purpose intensifier).
- In a desirable manner; so as one could wish; satisfactorily; favourably; advantageously.