Meaning of “hot up” - Learner’s Dictionary

hot up

UK informal phrasal verb with hot uk us /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)