play up

verb4

1. •
   To make or attempt to make something appear more important, likely, or obvious; to showcase or highlight.

   • For the audition, Nicole will play up her skill as a pianist by playing Jesu, Joy of Man's Desiring by Bach.
2. •
   (UK) To misbehave.

   • Children who do not receive enough attention may begin to play up.
   • The radar system is playing up again.
3. •
   To play (e.g. sport or music) more vigorously.

   • I can't hear the ukuleles at the back. Play up please!
4. •
   (slang) To be unfaithful to a lover; to cheat; used with on.

   • […] the young fulla Jack'd brought along looked like he might suit in an emergency, and what the fuck, Jack'd already said she weren't interested. Serve Rog right if she played up on him. — 1997