Only Daughter
noun
An alone (一人) daughter is a daughter with no other daughter siblings, making her the only daughter.
The readings are 一人 plus 娘 put together into one, single (daughter) word.
「何でのっけから彼女に一人娘が売春しているなんて言ったんだ?」「ごめん。軽率だったよ。」
"Why did you tell her that her only daughter is prostituting to begin with?" "I’m sorry. I spoke out of turn."