Revolutionary and Parisian saying rubbish (5)
I believe the answer is:
waste
'rubbish' is the definition.
(I know that rubbish can be written as waste)
'revolutionary and parisian saying' is the wordplay.
'revolutionary' is a reversal indicator.
'and parisian' becomes 'et' ('and' in French).
'saying' becomes 'saw' (saw is a kind of saying).
'et'+'saw'='etsaw'
'etsaw' in reverse letter order is 'WASTE'.
(Other definitions for waste that I've seen before include "Become gradually weaker" , "Detritus" , "unused" , "Use inefficiently or inappropriately" , "Refuse - to get thin" .)