adverb
for some time now; already; since long ago
Expresses that something has been the case for a while, often with a nuance of having felt or thought something for some time. Used in formal or written contexts.
かねがねお噂は伺っておりました。
I have heard about you for some time now.
その問題についてはかねがね疑問に思っていた。
I had been wondering about that issue for quite a while.