Objects to alien ways of thinking (4-3)
I believe the answer is:
mind-set
'ways of thinking' is the definition.
(someone's mind-set is their way of thinking)
'objects to alien' is the wordplay.
'objects to' becomes 'minds' (I've seen this in another clue).
'alien' becomes 'et' (extraterrestrial).
'minds'+'et'='MIND-SET'
(Other definitions for mind-set that I've seen before include "Habitual way of thinking" , "Characteristic mental attitude" , "Send Tim (anag.)" , "Fixed way of thinking" .)