Person betraying characteristic obstinacy resists at first (7)
I believe the answer is:
traitor
'person' is the definition.
(traitor is a kind of person)
'characteristic obstinacy resists at first' is the wordplay.
'characteristic' becomes 'trait' (a trait is a quality or characteristic).
'at first' indicates taking the first letters.
The initial letters of 'obstinacy resists' is 'or'.
'trait'+'or'='TRAITOR'
'betraying' is the link.
I am not very happy about this link. It may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for traitor that I've seen before include "Betrayer of a country" , "Betrayer, deceiver" , "Double-crosser" , "Turncoat" , "Rat displayed" .)