"The windows to the soul" (4)
I believe the answer is:
eyes
'the windows to the soul' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for eyes that I've seen before include "Ophthalmologist's speciality" , "Narrowly watches" , "(Paradoxical?) film with Cruise and Kidman" , "Regards -- features of a potato" , "front part of ship" .)