Gannet naturally raised is partly aerial (7)
I believe the answer is:
antenna
'aerial' is the definition.
(I know that aerial can be written as antenna)
'gannet naturally raised is partly' is the wordplay.
'is partly' indicates the answer is hidden within the clue (part of the clue is used).
'raised' says the letters should be written in reverse (going up in a down clue).
'annetna' is hidden in the letters of 'gannet naturally'.
'annetna' written backwards gives 'ANTENNA'.
(Other definitions for antenna that I've seen before include "Insect's sensory appendage" , "Aerial - insect feeler" , "could send out a message" , "Feature of dish" , "sensitive feeler" .)