Gain is the opposite of Reduce. Reduce is a synonym of Trim. Shelter is etymologically related to Trim. 
Employ is related to Job. Job is related to Payment. 
Gain <--Antonym--> Reduce <--Synonym--> Trim <--EtymologicallyRelatedTo-- Shelter 
Employ <--RelatedTo--> Job <--RelatedTo--> Payment 