Slow early bird doesn't finish work (5)
I believe the answer is:
largo
'slow' is the definition.
('largo' can be similar in meaning to 'slow')
'early bird doesn't finish work' is the wordplay.
'early bird' becomes 'lark' (I've seen this before).
'doesn't finish' means to remove the last letter.
'work' becomes 'go' ('go' can be a synonym of 'work').
'lark' with its last letter taken off is 'lar'.
'lar'+'go'='LARGO'
(Other definitions for largo that I've seen before include "Musically in slow tempo and dignified style" , "Slow and dignified tempo in music" , "at stately speed" , "Key -, Humphrey Bogart film" , "Deliberately" .)