Second ballistic missile thundering (8)
I believe the answer is:
strident
'thundering' is the definition.
'second ballistic missile' is the wordplay.
'second' becomes 's' (common abbreviation).
'ballistic missile' becomes 'trident' (I've seen this before).
's'+'trident'='STRIDENT'
(Other definitions for strident that I've seen before include "Harsh in tone" , "Harsh, grating" , "Unpleasantly loud and harsh" , "ear-piercing" , "Noisy" .)