Not simple (6)
I believe the answer is:
tricky
(Other definitions for tricky that I've seen before include "Crafty or difficult" , "Awkwardly difficult" , "Thorny" , "Crafty; needing skill" , "Complicated" .)
I believe the answer is:
tricky
(Other definitions for tricky that I've seen before include "Crafty or difficult" , "Awkwardly difficult" , "Thorny" , "Crafty; needing skill" , "Complicated" .)