couple of points, definition of a gust, last time I checked, was ten knots or more from mean wind speed. (the French, for reasons best known to themselves, always seem to like to include the maximum, as in "5 kts gusting 8 kts!)
Wind passed by atc when cleared to land is usually average over last two minutes - you can always ask for the "instant" winds.
Different operators have different guidance in their operations manuals, one I am familiar adds half of the total gust to the mean wind crosswind component when deciding to assess whether within cross wind limits.
Hope this helps