Faithful friend concealing Conservative party's latest fraudulence (8)
I believe the answer is:
quackery
'fraudulence' is the definition.
(a quack is a fraud)
'faithful friend concealing conservative party's latest' is the wordplay.
'faithful friend' becomes 'Quaker' (the Quakers are the Religious Society of Friends).
'concealing' is an insertion indicator.
'conservative' becomes 'C' (UK political abbreviation).
'latest' suggests the final letters.
The last letter of 'party' is 'y'.
'quaker' enclosing 'c' is 'quacker'.
'quacker'+'y'='QUACKERY'
(Other definitions for quackery that I've seen before include "Fraudulent medical practice" , "Medical pretensions" , "dodgy practice" , "phony business" , "Treating fraud" .)