Firm support for lethal striker (5)
I believe the answer is:
cobra
'lethal striker' is the definition.
'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 "a king, for example" , "Venomous snake, may be king" , "one leading charmed life?" , "hamadryad" , "Reptile (found in Cabinet Office Briefing Room A?)" .)