In itself; as it is; in its own way — meaning to accept something as appropriate to its nature or circumstances.
この料理は高級ではないが、材料の良さがそれなりに生きている。
This dish isn't high-class, but the quality of the ingredients shows in its own way.
彼はプロ並みではないが、それなりに役に立つ存在だ。
He's not on a professional level, but he's useful in his own way.
古い車だが、それなりに手入れがされている。
It's an old car, but it's been maintained appropriately for its condition.
Within one's capacity; within limitations — meaning 'to the extent possible' or 'appropriately given the circumstances'.
初心者でもそれなりに楽しめる講座だ。
It's a course that beginners can enjoy to an appropriate degree.
給料は多くないが、それなりに暮らしていける。
The salary isn't large, but it's enough to live on reasonably.
彼は努力したが、それなりの結果にしか結びつかなかった。
He tried, but it only led to results commensurate with his effort.