be in earnest
to really mean what you are saying, especially when expressing an intention or wish
in earnest
if something starts happening in earnest, it begins properly – used when it was happening in a small or informal way before

[TahlilGaran] Dictionary of Contemporary English ▲

in earnest
with full effort and attention.
Peace talks began in earnest after four days of bloody fighting in September.

Usage notes: usually used to emphasize a change from a period of less effort or attention:
The presidential campaign began in earnest on Labor Day.

[TahlilGaran] English Idioms Dictionary ▲

in earnest
sincerely
The young woman has been looking for a job in earnest since she graduated.

[TahlilGaran] English Idioms Dictionary ▲

in earnest
adv. or adj. phr. Seriously; in a determined way.
The beaver was building his dam in earnest.
Bill did his homework in earnest.
■ Often used like a predicate adjective. Sometimes used with "dead", for emphasis.
Betty's friends thought she was joking when she said she wanted to be a doctor, but she was in dead earnest.

[TahlilGaran] English Idioms Dictionary ▲