The most common and most likely answer to this crossword clue is the 7 letter word OPTIMUM
I've seen this crossword clue in The Times
O
P
T
I
M
U
M
More clues leading to the result OPTIMUM
- The best work, note, saying nothing
- Model wants time with single mother put to work
- Plump single mother, ideal
- Best to make a choice, one mother’s supporting
- Best pot I foolishly presented to old lady
- Oscar training a single parent to become model?
- It's best the writer's lodged by plump old lady
- Pick one parent as the best
- Agree to take part with mother withholding name? That’s for the best
- Plump single mother could be best
Buddy explains!

The straight part
We know that "The best" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case the best = optimum.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 OPTIMUM mean?
OPTIMUM noun- The best or most favorable condition, or the greatest amount or degree possible under specific sets of comparable circumstances.
- The best or most advantageous; surpassing all others.