mess around with (something)

to amuse yourself by doing or saying something that is likely to cause trouble.

I don't know if I'm dealing with a 14-year-old messing around with a computer or if I'm dealing with organized crime.

• be on the bottle
• be on the breadline
• be on the brink of
• be on the brink of doing something
• be on the cards
• be on the case
• be on the crest of a wave
• be on the [expensive/heavy/large etc.] side
• be on the expensive side
• be on the fiddle
• be on the fritz
• be on the game
• be on the heavy side
• be on the horns of a dilemma
• be on the large side
• be on the level
• be on the line
• be on the loose
• be on the march
• be on the mend
• be on the money
• be on the piss
• be on the ragged edge
• be on the razzle
• be on the receiving end