Apprentice outwardly dismissed for having been lazy (7)

'been lazy' is the definition.
Although both the answer and definition are past participle verbs, I cannot understand how one could define the other.

'apprentice outwardly dismissed for' is the wordplay.
I cannot quite see how this works, but
'apprentice' could be 'l' (as in a learner driver with L-plates on their car) and 'l' is found within the answer.
'dismissed' could be 'sacked' ('sack' can be a synonym of 'dismiss') and 'sacked' is found in the leftover letters.
No letters remain.
This may be the basis of the clue (or it may be nonsense).

'having' acts as a link.

Can you help me to learn more?