Stable employee maybe happy, heading off (3)
I believe the answer is:
lad
'stable employee' is the definition.
(lad can mean a stable lad)
'happy heading off' is the wordplay.
'happy' becomes 'glad' (similar in meaning).
'heading off' means to remove the first letter.
'glad' with its first letter taken away is 'LAD'.
'maybe' acts as a link.
(Other definitions for lad that I've seen before include "Boy, young man" , "Stable worker" , "Boy or youth" , "Chap, fellow" , "Shaver" .)