Gets into line, prepared for a roasting (7)
I believe the answer is:
dressed
'prepared for a roasting' is the definition.
(as in dressing meat for roasting)
I can't explain the remainder of the clue.
(Other definitions for dressed that I've seen before include "When you buy them crabs might be" , "Clothed" , "as a crab may be?" , "finery?" , "Put on clothes" .)