Meaning of “get up to sth” - Learner’s Dictionary

get up to sth

UK phrasal verb with get us uk /ɡet/ verb present participle getting, past tense got, past participle got, US gotten

to do something, especially something that other people think is wrong:

She's been getting up to all sorts of mischief lately.

(Definition of “get up to sth” from the Cambridge Learner’s Dictionary © Cambridge University Press)