Bulletproof with target moving (10)
I believe the answer is:
watertight
'bulletproof' is the definition.
(thesaurus)
'with target moving' is the wordplay.
'moving' is an anagram indicator.
'with'+'target'='withtarget'
'withtarget' with letters rearranged gives 'WATERTIGHT'.
(Other definitions for watertight that I've seen before include "Without loopholes" , "seaworthy" , "Impregnable" , "Impermeable - unbreakable" , "Proof against leaking" .)