Type of locks in frame of doors protecting study (6)
I believe the answer is:
dreads
'type of locks' is the definition.
(type of hair - locks can mean hair)
'frame of doors protecting study' is the wordplay.
'frame of' means to remove the middle letters (use the outside letters which frame the word).
'protecting' indicates putting letters inside.
'study' becomes 'read' (synonyms).
'doors' with its centre taken out is 'ds'.
'ds' enclosing 'read' is 'DREADS'.
'in' is the link.
(Other definitions for dreads that I've seen before include "Is terrified" , "Is in great fear of" , "Anticipates with horror" , "Strongly fears" , "Sadder (anag)" .)