Meaning of “smarten (sb/sth) up” - Learner’s Dictionary

smarten (sb/sth) up

phrasal verb with smarten uk us /ˈsmɑːtən/ verb

to make a person or place look more clean and tidy:

plans to smarten up the city centre

(Definition of “smarten (sb/sth) up” from the Cambridge Learner’s Dictionary © Cambridge University Press)