Crossword Genius

Compare efforts to protect a marine ecosystem (4)

Ross

I believe the answer is:

reef

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'a marine ecosystem' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how one could define the other.

'compare efforts to protect' is the wordplay.
'to protect' indicates the answer is hidden within the clue (the answer is protected by the clue).
'REEF' is hidden in the letters of 'compare efforts'.

Can you help me to learn more?

(Other definitions for reef that I've seen before include "Chain of rocks near the surface of the sea" , "Chain of rocks underwater" , "portion of sail" , "Submerged rocks" , "Submerged ridge of rock or coral near the surface" .)

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