Aerial insect upset girl (7)
I believe the answer is:
antenna
'aerial' is the definition.
(I know that aerial can be written as antenna)
'insect upset girl' is the wordplay.
'insect' becomes 'ant' (ant is a kind of insect).
'upset' shows that the letters should be reversed in order.
'girl' becomes 'anne' (girl's name).
'anne' in reverse letter order is 'enna'.
'ant'+'enna'='ANTENNA'
(Other definitions for antenna that I've seen before include "receiver" , "Feeling part" , "Insect's sensory appendage" , "one feels" , "connected to 41?" .)