From Longman Dictionary of Contemporary Englishfiddle around with something (also fiddle about with something British English) phrasal verb1 CHANGE/MAKE something DIFFERENTto move the parts of a machine in order to try to make it work or repair it I’ve been fiddling around with this old car for months but I still can’t get it to work.2 CHANGE/MAKE something DIFFERENTto make small unnecessary changes to something – used to show disapproval SYN mess around with Why did you let her fiddle about with the remote control? The bus company is always fiddling around with the schedules. → fiddle→ See Verb table
Examples from the Corpus
fiddle around with • I was fiddling around with a couple of tracks, trying various things.• Watching a kid fiddling around with fried bread.• Talking all the time she opened a few cupboards, then got a tin out and fiddled around with it.• She's always having the builders in to fiddle around with something or other.• Unfortunately there's no way to arrange text into columns without fiddling around with the tab settings. 