Cover leftovers with a plate, a lidded glass or steel container, or a beeswax or plant-wax cotton wrap. Buy no more cling film once the current roll runs out.
A household roll of cling film weighs around 60 to 90 g of plastic; a person using two or three rolls a year avoids roughly 200 g. The Ellen MacArthur Foundation's upstream-innovation framework puts elimination first: the best packaging is the packaging you never use.
The catch: beeswax wraps are not vegan, wear out in about a year and cannot be used for raw meat; a plate or container is the zero-cost option.