Sense organs in key essentially (4)

I believe the answer is:

eyes

'sense organs' is the definition.
(eye is a kind of sense organ)

'in key essentially' is the wordplay.
'in' says the answer is hidden in the clue.
'EYES' can be found hidden inside 'key essentially'.

(Other definitions for eyes that I've seen before include "Optical organs" , "They look" , "Potato seed-buds" , "Narrowly watches" , "Parts of needles" .)

I've seen this clue in The Irish Independent.

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