Weary author occasionally lacking inspiration (5)
I believe the answer is:
erato
'inspiration' is the definition.
(one of the muses in Greek mythology)
'weary author occasionally lacking' is the wordplay.
'occasionally lacking' indicates alternate letters (letters removed at regular intervals or occasions).
'weary'+'author'='wearyauthor'
The alternate letters of 'wearyauthor' are 'ERATO'.
(Other definitions for erato that I've seen before include "Source of poetic inspiration" , "Greek muse - orate (anag)" , "poetical inspiration" , "Muse of lyric love-poetry" , "Poet's muse" .)