It also depends on what it is that you can see in the pic that you are trying to clean out? If it is grime/water/oil all mixed together then as above just clean out and wipe down, however one of mine the PO had liberally applied grease to the area, no filled it, but given everything a good covering, which I just left in place as I couldn't see it doing any harm and if you clean it out next time you take it apart the are will have a thin layer of gearbox oil in it anyway, it will not stay clean and pristine.