Meaning of “hot up” - Learner’s Dictionary

hot up

UK informal phrasal verb with hot us uk /hɒt/ verb present participle hotting, past tense and past participle hotted

If a situation or event hots up, it becomes more exciting and more things start to happen:

The competition is really hotting up now.

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