Impudence visible from manner, vexatious (5)
I believe the answer is:
nerve
'impudence' is the definition.
(I know that impudence can be written as nerve)
'visible from manner vexatious' is the wordplay.
'visible from' indicates the answer is hidden within the clue.
'NERVE' can be found hidden inside 'manner vexatious'.
(Other definitions for nerve that I've seen before include "Bundles of fibres in the body that transmit instructions" , "Sensitive fibre in the body" , "Sauce" , "Sensory organ; bottle" , "Cord that carries instructions from brain to body" .)