Wiktionary
prep.phr. (context idiomatic with infinitive English) Making careful effort (to).
Usage examples of "at pains".
Because I paid attention, toady-like, to his proses, and was eager in studying his language, he assumed I was interested in his appalling country and its ways, and was at pains to educate me, as he saw it.
The most important is that the rich in London, though unprincipled, are at pains to conceal the fact, which makes them vulnerable.
He was at pains to tell me what he had been at when the snake got him, which was squatting among the rocks relieving himself.
He was at pains to tell me what he had been at when the snake got him, which was sauatting amone the rocks relieving himself.
Ebrard feared that he was come to claim a share in what Sir Eudo had left, and was at pains to show him that he had forfeited the old man's favour and his own filial rights.
At the foot of the deed I put the words `Veuve Lacoste,' but I had been at pains to disguise my handwriting.
Who had been at pains to give Harriet notions of self-consequence but herself?