get onto somebody/something phrasal verb (see also get)

1. SPEAK/WRITE TO SOMEBODY informal to speak or write to someone:
I’ll get onto my lawyer about this.

2. LEARN ABOUT SOMEBODY informal to find out about someone who has been doing something wrong:
How did the police get onto him?

3. BE ELECTED to be elected as a member of a committee, a political organization etc:
She was quite keen to get onto the management committee.

4. TALK ABOUT SOMETHING to begin to talk about a subject after you have been discussing something else:
After a few minutes they got onto the subject of the election.

5. DO SOMETHING informal to start dealing with something:
Right, I’ll get onto it straight away.

[TahlilGaran] Dictionary of Contemporary English ▲

get onto
{v.}, {informal}
1. To speak to (someone) roughly about something he did wrong; blame; scold.
Mrs. Thompson got on the girls for not keeping their rooms clean.

The fans got on the new shortstop after he made several errors.
Syn.: JUMP ON.
2. See: GET ALONG.
3. To grow older.
Work seems harder these days; I'm getting on, you know.

[TahlilGaran] English Idioms Dictionary ▲