Walk is the opposite of Fly. Fly is related to Movie. you are likely to find Sound in/at/on Movie. 
Mortgage is the opposite of Rent. Rent is related to Use. Use is related to Cut. 
Walk <--Antonym--> Fly <--RelatedTo--> Movie <--AtLocation-- Sound 
Mortgage <--Antonym--> Rent <--RelatedTo--> Use <--RelatedTo--> Cut 