Final job composing something to play at day's end... (4,4)
I believe the answer is:
last post
'something to play at day's end' is the definition.
I can't tell whether this defines the answer.
'final job composing' is the wordplay.
'final' becomes 'last' (synonyms).
'job' becomes 'post' (post is a kind of job).
'composing' means one lot of letters go next to another.
'last'+'post'='LAST POST'
Can you help me to learn more?
(Other definitions for last post that I've seen before include "missed by tardy correspondent" , "Bugle call for sunset or funeral" , "Final bugle call" , "Call for those retiring" , "passing notes from the military?" .)