This is the 872nd most frequent Ukrainian word.
кличко
"Кличко" is a Ukrainian surname.
In this sentence, 'Кличко' is used as a proper noun referring to the athlete.
Кличко є відомим українським боксером.
Klitschko is a famous Ukrainian boxer.
Here, 'кличко' refers to a simple exclamation or call for attention in Ukrainian.
Вони разом вигукували кличко, щоб привернути увагу.
They together shouted out a call to attract attention.
In this example, 'Кличко' again is a proper noun, referring to the person's likeness and name on the postcard.