Crossword Genius

Crew a carrier defending ocean cruiser? (5,3)

Ross

I believe the answer is:

manta ray

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

'ocean cruiser?' is the definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.

'crew a carrier defending' is the wordplay.
'crew' becomes 'man' (I've seen this before).
'carrier' becomes 'tray' (I've seen this before).
'defending' means one lot of letters goes inside another.
'a' placed within 'tray' is 'taray'.
'man'+'taray'='MANTA RAY'

Can you help me to learn more?

(Other definitions for manta ray that I've seen before include "large fish" , "Devilfish" .)

I've seen this clue in the Sydney Morning Herald.
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