Innocent cargo of vessel tracked northwards (7)

I believe the answer is:

artless

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

'innocent' is the definition.
(I've seen this in another clue)

'of vessel tracked northwards' is the wordplay.
'of' indicates the answer is hidden within the clue.
'northwards' shows that the letters should be reversed in order (in a down clue, letters go up or 'north').
'sseltra' can be found hidden inside 'vessel tracked'.
'sseltra' in reverse letter order is 'ARTLESS'.

'cargo' is the link.
I am not very happy about this link. It may belong to another bit of the clue.

Can you help me to learn more?

(Other definitions for artless that I've seen before include "Simple and natural in manner" , "Simple, unaffected" , "Natural - uncontrived" , "Free from cunning" , "Nave" .)

I've seen this clue in The Independent.

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