Starchy hem of Eleanor's first coat (6)

I believe the answer is:

primer

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'first coat' is the definition.
(I've seen this in another clue)

'starchy hem of eleanor's' is the wordplay.
'starchy' becomes 'prim' (I've seen this in another clue).
'hem of eleanor' becomes 'er' (I can't explain this - if you can you should believe this answer much more).
'prim'+'er'='PRIMER'

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(Other definitions for primer that I've seen before include "Initial coat of paint" , "explosive device" , "Basic teaching book" , "Sealant coat" , "Reading book" .)

I've seen this clue in The Telegraph.

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