Crossword Genius

This is thrown from the plane by which mothers returning (6)

Ross

I believe the answer is:

jetsam

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'this is thrown from' is the definition.
The definition suggests a singular noun which matches the answer.

'plane by which mothers returning' is the wordplay.
'plane' becomes 'jet' (jet plane).
'by which' is a charade indicator (letters next to each other).
'mothers' becomes 'mas' (ma is a kind of mother).
'returning' shows that the letters should be reversed in order.
'mas' back-to-front is 'sam'.
'jet'+'sam'='JETSAM'

'the' acts as a link.

Can you help me to learn more?

(Other definitions for jetsam that I've seen before include "Material flung overboard" , "Goods washed ashore from shipwreck" , "Ship's discharge" , "Discarded cargo" , "Items thrown overboard" .)

I've seen this clue in The Irish News.
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