Flinched (6)
I believe the answer is:
winced
'flinched' is the definition.
('wince' can be a synonym of 'flinch')
This is the entire clue.
(Other definitions for winced that I've seen before include "Made slight involuntary movement from pain or embarrassment" , "Grimaced slightly" , "Flinched, cringed" , "Flinched, made a face" .)