Endlessly tough for each general author (6,3)
I believe the answer is:
harper lee
'author' is the definition.
(author of To Kill a Mockingbird)
'endlessly tough for each general' is the wordplay.
'endlessly' means to remove the last letter.
'tough' becomes 'hard' (associated in meaning).
'for each' becomes 'per' (I've seen this before).
'general' becomes 'lee' (Robert E. Lee - US revolutionary commander).
'hard' with its final letter taken off is 'har'.
'har'+'per'+'lee'='HARPER LEE'
(Other definitions for harper lee that I've seen before include "American novelist" , "Author of Go Set a Watchman, d. 2016 -- paler here (anag)" .)