Shell fragments disrupt her plans (8)
I believe the answer is:
shrapnel
'shell fragments' is the definition.
(I've seen this in another clue)
'disrupt her plans' is the wordplay.
'disrupt' indicates anagramming the letters.
'her'+'plans'='herplans'
'herplans' with letters rearranged gives 'SHRAPNEL'.
(Other definitions for shrapnel that I've seen before include "Bits of shelling" , "Bomb or shell fragments" , "Projectile fragments" , "Pieces scattered after a shell explodes" , "Fall out from bomb" .)