Soothes (7)
(Other definitions for softens that I've seen before include "begins to warm" , "Relaxes" , "Makes less hard" , "Moderates" .)
(Other definitions for placates that I've seen before include "Calms down" , "'Appeases, mollifies (8)'" , "Assuages" .)
'soothes' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for calms that I've seen before include "Pacifies" , "Soothes" .)