Back in Idaho lady is welcome (5)
I believe the answer is:
aloha
'is welcome' is the definition.
(I've seen this before)
'back in idaho lady' is the wordplay.
'back' says the letters should be written in reverse.
'in' indicates the answer is hidden within the clue.
'ahola' is hidden in the letters of 'idaho lady'.
'ahola' reversed gives 'ALOHA'.
(Other definitions for aloha that I've seen before include "Welcome to Honolulu!" , "Hawaiian "ciao"" , "16 across in Hawaii" , "A Hawaiian welcome" , "A greeting in Hawaii" .)