Makes errors lacking an alternative (4)

I believe the answer is:

errs

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'makes' is the definition.
The answer and definition can be both related to thinking as well as being verbs in their -s form.
Maybe they are linked in a way I don't understand?

'errors lacking an alternative' is the wordplay.
'lacking' is a deletion indicator.
'an alternative' becomes 'or'.
'errors' with 'or' removed is 'ERRS'.

Can you help me to learn more?

(Other definitions for errs that I've seen before include "Slips up" , "Boobs" , "Is mistaken" , "Goes wrong" , "Sins" .)

I've seen this clue in The Globe and Mail.

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