The attitude is different in ascent (6)
I believe the answer is:
stance
'the attitude' is the definition.
(stance is a kind of attitude)
'different in ascent' is the wordplay.
'different in' is an anagram indicator (I've seen this in other clues).
'ascent' with letters rearranged gives 'STANCE'.
'is' acts as a link.
(Other definitions for stance that I've seen before include "driver preparing to strike" , "Posture; point of view" , "Position of the body or an attitude" , "One's physical or mental attitude" , "Upright posture" .)