From Hanoi to Mekong, travelling west, there's excitement (7)
I believe the answer is:
emotion
'excitement' is the definition.
(thesaurus)
'from hanoi to mekong travelling west' is the wordplay.
'from' says the answer is hidden in the clue.
'travelling west' is a reversal indicator.
'noitome' is hidden within 'hanoi to mekong'.
'noitome' reversed gives 'EMOTION'.
'there's' is the link.
(Other definitions for emotion that I've seen before include "reaction" , "Intense feeling" , "Mental agitation" , "Passion" , "A strong instinctive feeling" .)