Casual employee seen after leaving (7)
I believe the answer is:
offhand
'casual' is the definition.
(synonyms)
'employee seen after leaving' is the wordplay.
'employee' becomes 'hand' (hand is a kind of employee).
'seen after' says to put letters next to each other.
'leaving' becomes 'off' (as in 'I'm off').
'hand' after 'off' is 'OFFHAND'.
(Other definitions for offhand that I've seen before include "Casually rude" , "Cavalier" , "with a careless manner" , "Rudely casual; impromptu" , "Casual or curt, like discarded glove?" .)