Rear is a synonym of Back. Back is related to Rest. Rest is related to Recovery. 
Clear is related to Perception. Perception is related to Hear. Hear is related to Aids. 
Rear <--Synonym--> Back <--RelatedTo--> Rest <--RelatedTo--> Recovery 
Clear <--RelatedTo--> Perception <--RelatedTo--> Hear <--RelatedTo--> Aids 