Nouns ending in -té are usually feminine, but le député is masculine.
Député is one of the rare exceptions: learn it as it is.
Is député masculine or feminine?
ledéputéexception
The rule behind it
91.3% of -té nouns are feminine
In context
Notre député a argumenté contre le nouveau plan fiscal.
Our representative argued against the new tax plan.
Il avait servi comme député et sénateur.
He had served as a congressman and senator.
Il avait servi en tant que député et sénateur.
He had served as a congressman and senator.