Ambassador, eschewing seriousness in promotions, beams (10)

I believe the answer is:

headlights

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'beams' is the definition.
The definition and answer can be both man-made objects as well as being plural nouns.
Perhaps there's a link between them I don't understand?

'ambassador eschewing seriousness in promotions' is the wordplay.
'ambassador' becomes 'he' (His or Her Excellency).
'eschewing seriousness' becomes 'light' (I am not sure about this - if you are sure you should believe this answer much more).
'in' means one lot of letters goes inside another.
'promotions' becomes 'ads' (ad is a kind of promotion).
'light' inserted into 'ads' is 'adlights'.
'he'+'adlights'='HEADLIGHTS'

Can you help me to learn more?

I've seen this clue in The Telegraph.

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