Chain reaction starts melting lead protection rocker? (6)
I believe the answer is:
cradle
'protection rocker?' is the definition.
(as in a cradle rocking a baby)
'chain reaction starts melting lead' is the wordplay.
'starts' suggests taking the first letters.
'melting' indicates anagramming the letters.
The initial letters of 'chain reaction' is 'cr'.
'lead' with letters rearranged gives 'adle'.
'cr'+'adle'='CRADLE'
(Other definitions for cradle that I've seen before include "Bassinet" , "Hold tenderly" , "situation far from grave" , "'When the bough breaks, the . . . . . . will fall'" , "early bed" .)