Left date that’s too old (7)
I believe the answer is:
overage
'too old' is the definition.
(I've seen this before)
'left date' is the wordplay.
'left' becomes 'over' (I've seen this before).
'date' becomes 'age' (both can mean to get older).
'over'+'age'='OVERAGE'
'that's' acts as a link.
(Other definitions for overage that I've seen before include "Excess" , "Too old to qualify or a surplus of goods" , "Older than certain limit" , "Excessively old" , "Too old to be eligible" .)