Yes. Caulk will often cover 4 to 5mm, but if you need to caulk wider gaps than that it is possible to pack a sliver of expanded polystyrene packaging, or even polythene foam protective wrapping (the sort of thing eBay sellers seem to like - but NOT bubble wrap) into the gap to provide support for the caulk.
For a more "professional' support material you could always get hold of an appropriate size of something like Fossa Caulk Saver from the 'net or from a decorator centre such as Dulux Deco Centres, McDougall-Rose, etc. This is basically a closed cell foam cord made in a variety of diameters from about 3mm up to over 30mm which decorators use to pack gaps between skirtings and plasterwork (to a few millimetres below surface level) before applying the caulk. Amazingly, at least to me, I have come across professional decorators who have never come across such a product
For really big gaps (10/12mm and upwards) expanding foam can also be used as a backer, but it can't be used on very narrow gaps and it requires a very light touch (not to mention masking tape protection) to ensure that the foam doesn't go everywhere. So I wouldn't recommend that unless you can use foam judiciously