Firm support for hooded killer (5)
I believe the answer is:
cobra
'hooded killer' is the definition.
(I've seen this in another clue)
'firm support' is the wordplay.
'firm' becomes 'co' (a firm is a company).
'support' becomes 'bra' (a support for the breasts).
'co'+'bra'='COBRA'
'for' acts as a link.
(Other definitions for cobra that I've seen before include "Venomous snake, may be king" , "Venomous Asiatic and African elapid snake" , "Reptile (found in Cabinet Office Briefing Room A?)" , "Something with a hood" , "Poisoner" .)