Measuring device encountered by the queen (5)
I believe the answer is:
meter
'measuring device' is the definition.
(device for measuring something, eg a thermometer)
'encountered by the queen' is the wordplay.
'encountered' becomes 'met' ('meet' can be a synonym of 'encounter').
'by' is a charade indicator (letters next to each other).
'the queen' becomes 'ER' (Elizabeth Regina ie Queen Elizabeth).
'met'+'er'='METER'
(Other definitions for meter that I've seen before include "Something measuring" , "Device for measuring and recording" , "Measuring device, say for electricity usage" , "Device to measure quantity used of fluid, electricity etc" , "Device that measures, say, electricity usage" .)