Fights endless pests that are the most scattered (8)

I believe the answer is:

sparsest

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'the most scattered' is the definition.
(I've seen this before)

'fights endless pests' is the wordplay.
'fights' becomes 'spars' (sparring is a kind of fighting).
'endless' means to look at the middle letters.
The middle of 'pests' is 'est'.
'spars'+'est'='SPARSEST'

'that are' acts as a link.
This may not be correct. Some or all of it may be part of another bit of the clue.

Can you help me to learn more?

(Another definition for sparsest that I've seen is " Most scattered".)

I've seen this clue in The Irish Times.

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