Like Voltaire, for instance, showing annoyance over one chapter (6)
I believe the answer is:
gallic
'like voltaire for instance' is the definition.
(French author)
'annoyance over one chapter' is the wordplay.
'annoyance' becomes 'gall'.
'over' means one lot of letters go next to another.
'one' becomes 'i' (Roman numeral).
'chapter' becomes 'c' (abbreviation).
'gall'+'i'+'c'='GALLIC'
'showing' is the link.
(Other definitions for gallic that I've seen before include "Characteristic of the French" , "Pertaining to France" , "Of the French/France" , "Like certain wars" , "Typically French or of France" .)