That fugitive casual worker followed by us! (6)

I believe the answer is:
tempus
'that fugitive casual' is the definition.
I know nothing about this answer so I cannot judge whether it can be defined by this definition.
'worker followed by us' is the wordplay.
'worker' becomes 'temp' (temp is a kind of worker).
'followed by' is a charade indicator (letters next to each other).
'temp'+'us'='TEMPUS'
Can you help me to learn more?
(Another definition for tempus that I've seen is " Time flies - . . . . . . fugit".)
