A Parisian backing patent for a type of bomb (7)
I believe the answer is:
nuclear
'a type of bomb' is the definition.
(nuclear bomb)
'a parisian backing patent' is the wordplay.
'a parisian' becomes 'un' ('a' in French).
'backing' says the letters should be written backwards.
'patent' becomes 'clear' (synonyms).
'un' in reverse letter order is 'nu'.
'nu'+'clear'='NUCLEAR'
'for' is the link.
(Other definitions for nuclear that I've seen before include "basic family" , "Derived from fission or fusion" , "sort of family" , "Such power available" , "kind of war" .)