So I'm not in the air just to fly high! (4)
I believe the answer is:
soar
'to fly high' is the definition.
(soar up into the air)
'so i'm not in the air' is the wordplay.
'i'm' becomes 'i' (I've seen this in other clues).
'not in' indicates named letters should be taken away.
'air' with 'i' taken out is 'ar'.
'so'+'ar'='SOAR'
'just' is the link.
(Other definitions for soar that I've seen before include "Rise high in flight" , "rise dramatically" , "Fly high into the air" , "Fly high, Leicester river" , "Rise; sounds like painful" .)