Crossword Genius

Eats in, when Des is out (5)

Ross

I believe the answer is:

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'eats' is the definition.
(dining is a kind of eating)

'in when des is out' is the wordplay.
'when' becomes 'e' (I've seen this in other clues).
'des' becomes 'ds' (I can't justify this - if you can you should give a lot more credence to this answer).
'is out' indicates putting letters inside.
'in'+'e'='ine'
'ine' put into 'ds' is 'DINES'.

Can you help me to learn more?

(Another definition for dines that I've seen is "Eats".)