Out of shape and old, fight for Japanese packed lunch (5,3)
I believe the answer is:
bento box
'japanese packed lunch' is the definition.
I don't know anything about this answer so I can't tell whether it can be defined by this definition.
'out of shape and old fight' is the wordplay.
'out of shape' becomes 'bent' (I've seen this in another clue).
'and' means one lot of letters go next to another.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'fight' becomes 'box' (boxing is a kind of fighting).
'bent'+'o'+'box'='BENTO BOX'
'for' acts as a link.
Can you help me to learn more?
(Another definition for bento box that I've seen is " food container".)