WordNet
be at pains
v. try very hard to do something [syn: take pains]
Usage examples of "be at pains".
And therefore, my infant, you must not only bear with her folly, but you must be at pains to cause her no trouble.
The postscript specified that she was to take her fur jacket, that she was to dress entirely in black (entirely was underlined), and was to be at pains to make up and perfume herself as at Roissy.