The most common and most likely answer to this crossword clue is the 9 letter word BATHSHEBA
B
A
T
H
S
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B
A
More clues leading to the result BATHSHEBA
- Biblical 21, clean, with sex appeal, ensnaring Hebrew
- Male in Sabbath-breaking who found lover in Troy
- David's wife in university city, the woman with arts degree
- Hardy female graduates framing article about mum
- Wife of Uriah Heep, initially taken in by very eccentric male graduate
- Man, during Sabbath, fancied a scriptural woman
- That woman in tub with graduate — female partner in affair
- David’s wife has bath be arranged
- David’s wife breaking Sabbath with the guy inside
- She gets into tub with a couple of bachelors and David's wife
Buddy explains!

The straight part
We know that "female partner in affair" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case female partner in affair = bathsheba.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.