Leaves out-of-date, old tin cans (6,2)
I believe the answer is:
passes on
'leaves' is the definition.
(passing on is a kind of leaving)
'out-of-date old tin cans' is the wordplay.
'out-of-date' becomes 'passe' (synonyms).
'old' becomes 'o' (abbreviation).
'tin' becomes 'Sn' (Sn is the chemical symbol for tin).
'cans' indicates putting letters inside (to can could mean to contain).
'o' put inside 'sn' is 'son'.
'passe'+'son'='PASSES ON'
(Other definitions for passes on that I've seen before include "Hands to the next person" , "graduates" , "Dies; transmits" .)