Nouns ending in -sion are feminine.
The suffix forms abstract nouns of action or state.
Is pression masculine or feminine?
lapression
The rule behind it
100% of -sion nouns are feminine
In context
Ne cède pas à la pression des pairs.
Don't give in to peer pressure.
Je ne veux pas te mettre la pression.
I don't want to pressure you.
Je ne travaille pas bien sous la pression.
I don't work well under pressure.