Missile making a terrible crater (6)
I believe the answer is:
tracer
'missile' is the definition.
(I've seen this before)
'a terrible crater' is the wordplay.
'a terrible' indicates anagramming the letters.
'crater' anagrammed gives 'TRACER'.
'making' acts as a link.
(Other definitions for tracer that I've seen before include "trail of light" , "beast to tow" , "Bullet whose track can be seen - element tracking radiation" , "Missile" , "He's managed to find" .)