Little horseman's time after work (9)
I believe the answer is:
weeknight
'time after work' is the definition.
(time after the working day)
'little horseman's' is the wordplay.
'little' becomes 'wee' (similar in meaning).
'horseman' becomes 'knight' (knight on horseback).
'wee'+'knight'='WEEKNIGHT'
(Other definitions for weeknight that I've seen before include "Part of 67 [SENNIGHT]" , "appears between working days" , "time to sleep after work" , "Friday even, for example" , "Bit of time" .)