Prime parts of London avoided panelling scandal, exposing negligence (5)
I believe the answer is:
lapse
'negligence' is the definition.
(a lapse in responsibility)
'prime parts of london avoided panelling scandal exposing' is the wordplay.
'prime parts of' says to take the initial letters.
The first letters of 'london avoided panelling scandal exposing' is 'LAPSE'.
(Other definitions for lapse that I've seen before include "Become void, expire" , "Slip-up" , "Brief decline from high standards" , "Passing - mistake" , "Brief slip; fall from faith" .)