Welcome in Idaho largely sent up (5)
I believe the answer is:
aloha
'welcome' is the definition.
(I've seen this before)
'in idaho largely sent up' is the wordplay.
'in' indicates a hidden word.
'sent up' says the letters should be written in reverse.
'ahola' can be found hidden inside 'idaho largely'.
'ahola' back-to-front is 'ALOHA'.
(Other definitions for aloha that I've seen before include "Welcome to Honolulu!" , "16 across in Hawaii" , "A Hawaiian welcome" , "Hi! in Honolulu" , "Hawaiian farewell" .)