up on

up on - knowledgeable about or up to date with things

up one's sleeve

to have a secret idea or plan

up the creek

up the creek - in serious trouble, often financially

up to

up to - doing something (usually secretive)

up to the mark

good enough

upbeat

to be positive about something

uplifting

uplifting - making you feel happy and inspired

up-my-street

something just right for me

uproar

dissent

uptight

uptight - very formal, nervous or strained