I am trying to click on size from drop down from this particular website, but I'm not able to do that.
size = wait.until(EC.invisibility_of_element_located((By.TAG_NAME, 'UK 6'))).click();
You can find the element by searching on whether the element contains text "UK 6". The XPATH for finding the element would be:
So the code would be:
wait.until(EC.visibility_of_element_located((By.XPATH, '//li[contains(.,'UK 6')]'))).click()