Red spot exercises each with it needing treatment (8)

I believe the answer is:

petechia

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'red spot' is the definition.
The definition suggests a singular noun which matches the answer.

'exercises each with it needing treatment' is the wordplay.
'exercises' becomes 'pe' (Physical Education class).
'with' says to put letters next to each other.
'needing treatment' indicates an anagram (I've seen 'needs treatment' mean this (letters must be processed or treated)).
'each'+'it'='eachit'
'eachit' with letters rearranged gives 'techia'.
'pe'+'techia'='PETECHIA'

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I've seen this clue in The Independent.

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