Defect following piece of legislation (4)
I believe the answer is:
flaw
'defect' is the definition.
(synonyms)
'following piece of legislation' is the wordplay.
'following' becomes 'f.' (used when citing page numbers etc).
'piece of legislation' becomes 'law' (I've seen this in another clue).
'f'+'law'='FLAW'
(Other definitions for flaw that I've seen before include "sudden rush" , "Imperfection or blemish" , "Fault, blemish" , "(Make) defect(ive)" , "failing" .)