Learner given promotion is a stable employee (3)
I believe the answer is:
lad
'a stable employee' is the definition.
(lad can mean a stable lad)
'learner given promotion' is the wordplay.
'learner' becomes 'l' (as in a learner driver with L-plates on their car).
'given' is a charade indicator (letters next to each other).
'promotion' becomes 'ad' (short for advert).
'l'+'ad'='LAD'
'is' acts as a link.
(Other definitions for lad that I've seen before include "Boy or youth" , "A young chap into ballads" , "Stable worker" , "Son" , "Shaver" .)