Starting a trip but now our Dad is lost (7-5)

I believe the answer is:

outward bound

I'm a little stuck... Click here to teach me more about this clue!

'starting a trip but now our dad is lost' is the definition.
I can't tell whether this definition defines the answer.

'but now our dad is lost' is the wordplay.
'is lost' indicates an anagram.
'but'+'now'+'our'+'dad'='butnowourdad'
'butnowourdad' is an anagram of 'OUTWARD-BOUND'.

Can you help me to learn more?

(Other definitions for outward bound that I've seen before include "Leaving port" , "Going away from home" .)

I've seen this clue in The Everyman puzzle in The Observer.

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