Poor plasma set is quite unsuitable (10)

I believe the answer is:

malapropos

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'quite unsuitable' is the definition.
'malapropos' can be an answer for 'unsuitable' (I've seen this before). I'm not certain of the 'quite' bit.

'poor plasma set' is the wordplay.
'set' indicates an anagram (instruction to set the letters).
'poor'+'plasma'='poorplasma'
'poorplasma' is an anagram of 'MALAPROPOS'.

'is' acts as a link.

Can you help me to learn more?

(Other definitions for malapropos that I've seen before include "not fitting" , "inappropriate" , "Unsuitable" , "out of place" .)

I've seen this clue in The Everyman puzzle in The Observer.

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