Clyde asks the player to bring them 20 crab-apples, "to fill a barrel," although the player does not need to fill the barrel themselves. Unlike some similar quests, if the player already has 20 or more crab-apples, Clyde doesn't notice. The player must still end the conversation and then start a new conversation for Clyde to give the player the reward.
Crab-apples are found on the hill North of Breezy River Farm. To get it, bring the Gnome (Gloia) to the rock, and look out for a spot to repair. There will then be a ladder you need to jump on to reach the plateau with the crab-apples.
On the plateau, there's a security robot that throws rocks, knocking the player back, while also hitting the crab-apple trees, allowing for the fruit to be collected.
When complete, Clyde gives the player an Old Boot, which appears to be a gag item that does not stay in the inventory, and then gives the player the Shield artifact.