A soldier turned in turned out to have departed (9)

'departed' is the definition.
('digress' can be a synonym of 'depart')

'a soldier turned in turned' is the wordplay.
'a soldier' becomes 'GI' (GI can mean a US soldier).
'turned' shows that the letters should be reversed in order.
'in' means one lot of letters goes inside another.
'turned' becomes 'dressed' (dressing is a kind of turning).
'gi' in reverse letter order is 'ig'.
'ig' placed inside 'dressed' is 'DIGRESSED'.

'out to have' is the link.
This may not be right. Some or all of it may belong to another bit of the clue.

Can you help me to learn more?