Extra expected is late arriving (7)
I believe the answer is:
overdue
'late arriving' is the definition.
(I've seen this before)
'extra expected' is the wordplay.
'extra' becomes 'over'.
'expected' becomes 'due' (I've seen this before).
'over'+'due'='OVERDUE'
'is' is the link.
(Other definitions for overdue that I've seen before include "Later than expected" , "(Of library books) late" , "Belated" , "Later than the appointed time, as for bill payment" , "Past the ETA" .)