Showing regret about limits of curative magic (7)
I believe the answer is:
sorcery
'magic' is the definition.
(I know that sorcery is a type of magic)
'showing regret about limits of curative' is the wordplay.
'showing regret' becomes 'sorry' (I've seen this before).
'about' means one lot of letters goes inside another.
'limits of' suggests removing the centre.
'curative' with its centre removed is 'ce'.
'sorry' enclosing 'ce' is 'SORCERY'.
(Other definitions for sorcery that I've seen before include "Black magic" , "Necromancy" , "devilish practices" , "Magic; witchcraft" , "practice being aligned with the devil?" .)