Linkage bushes, righty the remote rod (thats rthe black steel rod that goes from the gear lever to the box selector arm).
At the box ends theres a bush, its a metal cylinder thing, about 1cm long, it has a knurled finish on the outside. This slips through the silver arm from the box anbd through the remote rod. Over this and the remote rod goes the plastic bit of the bush.
This bush wears as its always beign rubbed against, it doesnt spin so it only wears in the area where its loaded. 0.5mm of wear may not mean a lot, but at the lever this magnifioed a million times and makes slection tricky etc.
Anyway, get under the car, if you have the plastic guard take it off, then cut the cable tie around the rubber gaieter, if its not been touched be prepared for water to squirt out at you. Grab the tag and lift it over the bolt. Then 2 13mm spanners to loosen the nut and bolt. Pop the bolt out.
Now you can replace the bushges. Use some new grease on them. Pull the gaiter back over (I hate that bit, especially if its covered in grease) and use a new cable tie or something, or dont bother at all, whatever suits.
A new clutch means a new relase bearing etc, if it doesnt then go somewhere where they dont wear hats and carry guns and talk like John Wayne.
Also a clutch doesnt need to slip etc. If its tricky to get into gear its probably sticking, when it gets hot the clutch isnt releasing fully or the plates warped.
You have chanegd the cable havent you?