Mess around (with) (6)
I believe the answer is:
tinker
'mess around with' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for tinker that I've seen before include "Make trivial adjustments - itinerant tradesman" , "Person who travels around doing repairs" , "Potter - kettle mender" , "Mender of pots and pans" , "Kettle-mender" .)