Spanish gentlemen surrounding square detectors (7)

I believe the answer is:

sensors

'detectors' is the definition.
('sensor' can be a synonym of 'detector')

'spanish gentlemen surrounding square' is the wordplay.
'spanish gentlemen' becomes 'senors' (I've seen this in another clue).
'surrounding' indicates putting letters inside.
'square' becomes 's' (abbreviation).
'senors' enclosing 's' is 'SENSORS'.

(Another definition for sensors that I've seen is " Devices to receive signals or stimuli".)

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

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