Course ahead involving Caspian? (3)

I believe the answer is:

sea

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'caspian?' is the definition.
Both the answer and definition are adjectives.
Maybe they are linked in a way I don't understand?

'course ahead involving' is the wordplay.
'involving' indicates the answer is hidden within the clue (I've seen 'involves' mean this).
'SEA' is hidden within 'course ahead'.

Can you help me to learn more?

(Other definitions for sea that I've seen before include "E.g Aral or Weddell" , "that's easily reached from Dover?" , "Cause of flooding" , "Part of ocean" , "North, say" .)

I've seen this clue in The Sun.

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