Remaining bits reused, I gathered (7)
I believe the answer is:
residue
'remaining bits' is the definition.
'reused i gathered' is the wordplay.
'gathered' is an anagram indicator.
'reused'+'i'='reusedi'
'reusedi' with letters rearranged gives 'RESIDUE'.
(Other definitions for residue that I've seen before include "What remains of something" , "What's left" , "Something left over" , "rest" , "Dire use of the remainder" .)