Satisfied customer wearing heart on sleeve? (4)

I believe the answer is:

sure

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'satisfied customer' is the definition.
'sure' can be an answer for 'satisfied' (thesaurus). I am not certain of the 'customer' bit.

'wearing heart on sleeve?' is the wordplay.
'wearing' becomes 'erosive' (I've seen this in another clue).
'heart' indicates the central letters.
'on sleeve?' becomes 'ure' (I can't explain this - if you can you should believe this answer much more).
The middle letter of 'erosive' is 's'.
's'+'ure'='SURE'

Can you help me to learn more?

(Other definitions for sure that I've seen before include "Confident sort of ruse" , "Agreed" , "Certain to be a ruse" , "Positive" , "Feeling no doubt" .)

I've seen this clue in The Independent.

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