Malicious blogger? Right to block impact (5)
I believe the answer is:
troll
'malicious blogger?' is the definition.
(as in an internet troll)
'right to block impact' is the wordplay.
'right' becomes 'r' (common abbreviation).
'to block' is an insertion indicator (block can mean to fill a hole in something).
'impact' becomes 'toll' (the toll something takes).
'r' put into 'toll' is 'TROLL'.
(Other definitions for troll that I've seen before include "Creature from Norse mythology" , "Fairytale monster" , "Dwarfish creature" , "Ugly dwarf or giant" , "Draw baited line, to lure fish" .)