One feels soldier needs girl back (7)
I believe the answer is:
antenna
'one feels' is the definition.
(I've seen this before)
'soldier needs girl back' is the wordplay.
'soldier' becomes 'ant' (soldier is a type of ant).
'needs' says to put letters next to each other.
'girl' becomes 'anne' (girl's name).
'back' says the letters should be written in reverse.
'anne' reversed gives 'enna'.
'ant'+'enna'='ANTENNA'
(Other definitions for antenna that I've seen before include "could send out a message" , "connected to 41?" , "Insect's sensory appendage" , "sensitive feeler" , "Feature of dish" .)