Not entirely logical — often up in the air (5)
I believe the answer is:
aloft
'up in the air' is the definition.
(aloft means above or overhead)
'not entirely logical often' is the wordplay.
'not entirely' indicates the answer is hidden within the clue.
'ALOFT' is hidden in the letters of 'logical often'.
(Other definitions for aloft that I've seen before include "Animistic cult" , "flying?" , "up the mast" , "Above - on top" , "at high altitude" .)