Dares to alter scans (5)
I believe the answer is:
reads
'scans' is the definition.
('read' can be a synonym of 'scan')
'dares to alter' is the wordplay.
'to alter' indicates anagramming the letters.
'dares' anagrammed gives 'READS'.
(Other definitions for reads that I've seen before include "Peruses" , "Understands written language" , "Studies (at university)" , "Scans" , "Looks at and undertsands the written word" .)