Crossword Genius

What initiates disquiet about fellow in computing etc for certain (8)

Ross

I believe the answer is:

definite

'certain' is the definition.
(similar in meaning)

I cannot understand how the rest of the clue works.

(Other definitions for definite that I've seen before include "Sure, certain" , "Certain or explicit" , "Positive, certain" , "Unmistakable" , "Certain, decisive" .)

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