Course ahead involving Atlantic? (3)
I believe the answer is:
sea
'atlantic?' is the definition.
(atlantic is a kind of sea)
'course ahead involving' is the wordplay.
'involving' indicates the answer is hidden within the clue (I've seen 'involves' mean this).
'SEA' can be found hidden inside 'course ahead'.
(Other definitions for sea that I've seen before include "The tide" , "North, say" , "Large expanse of water" , "It's stocked with fish" , "The main" .)