Relents (6)
(Other definitions for abates that I've seen before include "Slacks off" , "'Lets up, dies away (6)'" , "Grows less intense" , "Goes down like storm" , "Diminishes" .)
'relents' is the definition.
(I've seen this in another clue)
This is all the clue.
(Another definition for lets up that I've seen is " Abates, eases up".)