Sea hazard for elderly carer? (4,5)

I believe the answer is:

grey nurse

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'sea hazard' is the definition.
I don't know anything about this answer so I can't tell whether it can be defined by this definition.

'elderly carer?' is the wordplay.
'elderly' becomes 'grey' (I've seen this in other clues).
'carer?' becomes 'nurse' (I've seen this before).
'grey'+'nurse'='GREY NURSE'

'for' acts as a link.

Can you help me to learn more?

(Another definition for grey nurse that I've seen is " shark".)

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

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