Look — one's taken in by a conjuror ultimately (3)
I believe the answer is:
air
'look' is the definition.
(something might have a certain air or look)
'one's taken in by a conjuror ultimately' is the wordplay.
'one' becomes 'i' (Roman numeral).
'taken in by' means one lot of letters goes inside another.
'ultimately' indicates one should take the final letters.
The final letter of 'conjuror' is 'r'.
'a'+'r'='ar'
'i' placed inside 'ar' is 'AIR'.
(Other definitions for air that I've seen before include "Display" , "in which birds fly around" , "Ventilate, give voice to" , "Gas mix surrounding the earth" , "Mix of gases surrounding the earth" .)