Having a go is troublesome (6)
I believe the answer is:
trying
I believe this is a double definition.
'having a go' is the first definition.
(having a go at something is trying it)
'troublesome' is the second definition.
(I've seen this before)
'is' acts as a link.
(Other definitions for trying that I've seen before include "Hard to endure" , "responsibility of the first Baron Jeffreys of Wem" , "undertaking" , "Making attempts" , "Attempting or irritating" .)