Note travellers climbing without principles (6)
I believe the answer is:
amoral
'without principles' is the definition.
(I've seen this before)
'note travellers climbing' is the wordplay.
'note' becomes 'la' (musical note as in do-re-mi).
'travellers' becomes 'Roma' (Romani people).
'climbing' says the letters should be written backwards (in a down clue, letters climb up).
'la'+'roma'='laroma'
'laroma' back-to-front is 'AMORAL'.
(Other definitions for amoral that I've seen before include "Unscrupulous" , "Unprincipled" , "Without sense of right and wrong" , "Lacking sense of decency" , "Ignoring what's right and wrong" .)