Withdraw demand about heartless teacher (7)
I believe the answer is:
extract
'withdraw' is the definition.
(I know that extract is a type of withdraw)
'demand about heartless teacher' is the wordplay.
'demand' becomes 'exact' (synonyms).
'about' is an insertion indicator.
'heartless' says to hollow out the word (remove centre letters).
'teacher' with its middle taken out is 'tr'.
'exact' placed around 'tr' is 'EXTRACT'.
(Other definitions for extract that I've seen before include "Cutting" , "Remove by force" , "Short piece" , "Short passage from a longer work" , "Take or pull out - say a tooth" .)