Keep gulley clear.

Hedgehog brush guard

Fill a bucket with hot water this will help breakdown any grease or help move any other unwanted nastys you can add a little bleach to or dish soap to help if it’s badly built up with crap

You can put drain unblocker down it to keep it clear

Put a mesh for leaves

It shouldn't really be getting blocked, as most gullys are weight assisted and have the outlet at the top, as this would run into foul drainage any off the shelf drainage unblocker would help keep the run clear, or popping off the grid and getting the silt/detergent out regularly would help

Bleach and leave for around half hour then wash down with hot boiling water