Bomb fragments ruined her plans (8)
I believe the answer is:
shrapnel
'bomb fragments' is the definition.
(I've seen this before)
'ruined her plans' is the wordplay.
'ruined' is an anagram indicator.
'her'+'plans'='herplans'
'herplans' anagrammed gives 'SHRAPNEL'.
(Other definitions for shrapnel that I've seen before include "Exploding shell fragments" , "Flying debris" , "Pieces scattered after a shell explodes" , "Metal bomb fragments" , "Colloquially, small change" .)