Leather is a type of Material. Material is related to Clay. Clay is a type of Soil. Soil is related to Plant. 
Current is the opposite of Back. Back is the opposite of Face. Face is related to Lip. Lip is related to Stiff. 
Leather --IsA--> Material <--RelatedTo--> Clay --IsA--> Soil <--RelatedTo--> Plant 
Current <--Antonym--> Back <--Antonym--> Face <--RelatedTo--> Lip <--RelatedTo--> Stiff 