Bad habits, clinging to old opinions (6)
I believe the answer is:
voices
'opinions' is the definition.
(voice can mean an opinion or perspective)
'bad habits clinging to old' is the wordplay.
'bad habits' becomes 'vices' (I've seen this in another clue).
'clinging to' means one lot of letters goes inside another.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'vices' placed around 'o' is 'VOICES'.
(Other definitions for voices that I've seen before include "Speaks" , "Sounds of people" , "They may be audible" , "Expressed opinions; utters" .)