Clue: Isn't it possible a Python antihero's someone from Santander? (10)
Answer: CANTABRIAN
Explanation: Isn't it possible a Python antihero's someone from Santander? (10)
A charade of CAN'T ('isn't it possible') plus 'a' plus BRIAN ('Python antihero' – a reference to the film 'Life of Brian'). Santander is the capital of the region of Cantabria in Spain.