。
I asked him point-blank.
Literal
Single-sword-straight-entry [adverbial-に] asked-[insistence-よ].
単刀直入 is a 四字熟語 (four-character compound) literally 'entering directly with a single sword drawn' — metaphorically 'straightforwardly, without beating around the bush, point-blank.' The adverbial に marks it as modifying 尋ねる ('to ask, inquire'). A vivid literary idiom turned common expression.