Back where witch lived — she heartless (7)
I believe the answer is:
endorse
'back' is the definition.
(back can mean to support or endorse)
'lived she heartless' is the wordplay.
'lived' becomes 'endor' (I can't justify this - if you can you should believe this answer much more).
'heartless' says to hollow out the word (remove centre letters).
'she' with its centre taken out is 'se'.
'endor'+'se'='ENDORSE'
'where witch' acts as a link.
This may not be correct. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for endorse that I've seen before include "Back, sanction" , "Give one's approval to" , "Sore end (anag.)" , "Ratify" , "Give backing to" .)