Crossword Genius

One offering a prune, that used to bring the tea? (7)

Ross

I believe the answer is:

clipper

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'prune that used to bring the tea?' is the definition.
Although both the answer and definition are singular nouns, I can't understand how they can define each other.

'one offering a' is the wordplay.
'one offering' becomes 'clip' (I can't explain this - if you can you should believe this answer much more).
'a' becomes 'per'.
'clip'+'per'='CLIPPER'

Can you help me to learn more?

(Other definitions for clipper that I've seen before include "Fast commercial sailing ship" , "Fast sailing ship of former times" , "that has slight collision with another?" , "Cutter" , "used to dock" .)

I've seen this clue in The Times.
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