Gradually destroy heartless expensive nursing staff (5)
I believe the answer is:
erode
'gradually destroy' is the definition.
(I've seen this before)
'heartless expensive nursing staff' is the wordplay.
'heartless' says to hollow out the word (remove centre letters).
'nursing' indicates putting letters inside.
'staff' becomes 'rod' (I've seen this before).
'expensive' with its middle taken out is 'ee'.
'ee' placed around 'rod' is 'ERODE'.
(Other definitions for erode that I've seen before include "fragment" , "go to pieces!" , "Corrode" , "Eat away" , "Slowly remove" .)