Notice a character, say (3)
I believe the answer is:
see
'notice' is the definition.
(notice can mean to spot or see)
'a character say' is the wordplay.
'a character' becomes 'c'.
'say' indicates a 'sounds like' (homophone) clue.
'c' is a homophone of 'SEE'.
(Other definitions for see that I've seen before include "Rome, notably" , "Consider; diocese" , "Perceive; diocese" , "Visualise" , "Glimpse; get" .)