Shield nurse carrying a head covering backwards (8)
I believe the answer is:
carapace
'shield' is the definition.
(I've seen this before)
'nurse carrying a head covering backwards' is the wordplay.
'nurse' becomes 'care' (to nurse someone is to care for them).
'carrying' is an insertion indicator.
'head covering' becomes 'cap'.
'backwards' is a reversal indicator.
'cap' backwards is 'pac'.
'a'+'pac'='apac'
'care' placed around 'apac' is 'CARAPACE'.
(Other definitions for carapace that I've seen before include "soft top? Hardly" , "Shell on back of tortoise or crustacean" , "Thick outer shell of tortoises, crabs etc" , "Hard shell of tortoise, crab etc" , "Pace a car around a shell, of a tortoise say" .)