Traveller is sensible to skip capital of Tunisia (5)
I believe the answer is:
nomad
'traveller' is the definition.
(nomad is a kind of traveller)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for nomad that I've seen before include "A member of a wandering tribe" , "Traveller with no permanent home" , "drifter" , "One keeps moving" , "being domestically unstable" .)