A girl about ten, one feels (7)
I believe the answer is:
antenna
'one feels' is the definition.
(an antenna feels things)
'a girl about ten' is the wordplay.
'a girl' becomes 'anna' ().
'about' indicates putting letters inside.
'anna' enclosing 'ten' is 'ANTENNA'.
(Other definitions for antenna that I've seen before include "Feeling part" , "receiver" , "Aerial - insect feeler" , "Transmitting aerial" , "could send out a message" .)