First remove the nib and feed together.
Grip the nib and feed together with your thumb and finger, pull out from the nib unit. If it is stuck with dried ink, give the unit a soak in warm plain tap water. A slight wiggle of the nib and feed will bring it clear. Do not use force.
Clean the feed in warm water, use a soft toothbrush if needed. You can also leave it to soak overnight. No need for detergent or cleaning sovents of any kind.