Slack lovers finally woke up, but were late for work, probably? (9)
I believe the answer is:
overslept
'late for work probably?' is the definition.
I can't judge whether this defines the answer.
'slack lovers finally woke up but' is the wordplay.
'slack' indicates an anagram (a slack or relaxed spelling of the letters).
'finally' indicates one should take the final letters.
The last letters of 'woke up but' are 'ept'.
'lovers' is an anagram of 'oversl'.
'oversl'+'ept'='OVERSLEPT'
'were' acts as a link.
Can you help me to learn more?
(Other definitions for overslept that I've seen before include "Was late rising" , "Failed to rise on time" .)