It should not be necessary to remove the outer cover to disconnect the clutch cable (although I guess it can depend on the shape of the cable nipple?) but it can be a bit awkward to do.
First ensure that the clutch cable is completely disconnected from the handlebar lever so that you have lots of slack on the inner cable, it should then be possible to pull the nipple down until it clears the fork, then hold the nipple with some needle nosed pliers, a slight twist and a pull should free it, the fork may need to be held up with a finger or a small screwdriver to give enough clearance as you do this, and do the reverse to refit it.
If that does not do it then slacken off the clutch centre adjuster nut and then unscrew the adjuster a few turns (after first screwing it in to check the adjuster setting) but don't remove the adjuster completely as the lifter arm (that the cable connects to) can drop out of position.
A worthwhile modification is to grind a small amount of metal from the fork ends if you do take the outer cover off, as that makes the job of removing/replacing the cable a lot easier the next time you need to do it.