noun, noun which may take the genitive case particle 'no'
best of one's time; greatest of the age; peerless
Used to describe someone or something that is considered the best in their era or generation. Often used in formal or literary contexts.
彼は当代一のピアニストと評されている。
He is acclaimed as the greatest pianist of our time.
この作品は当代一の傑作だ。
This work is a masterpiece of the age.
Means 'unparalleled in the present age'; 当代一 is more common and less emphatic.
Compound of 当代 (tōdai, 'the present age') and 一 (ichi, 'one' or 'first'), literally 'number one of the present age'.