monkey about with (something)

phrasal verb

monkeyed about with; monkeying about with; monkeys about with (something)

British, informal

1

: to use or do (something) in a way that is not very serious

He enjoys monkeying about with his car's engine.

2

: to handle or play with (something) in a careless or foolish way

You shouldn't be monkeying about with dangerous chemicals.