Leading light left before main service (7)

I believe the answer is:

lantern

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'leading light' is the definition.
(I've seen this before)

'left before main service' is the wordplay.
'left' becomes 'l' (common abbreviation).
'before' becomes 'ante' (I've seen this in other clues).
'main service' becomes 'rn' (abbreviation for Royal Navy. I am not sure about the 'main' bit.).
'l'+'ante'+'rn'='LANTERN'

Can you help me to learn more?

(Other definitions for lantern that I've seen before include "Encased light" , "Enclosed light" , "Transparent case for candle" , "outside D [DECORATION]" , "Light in a protective casing" .)

I've seen this clue in The Sun.

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