Commercial interrupts fight - it's boring (7)
I believe the answer is:
bradawl
'boring' is the definition.
(I've seen this before)
'commercial interrupts fight' is the wordplay.
'commercial' becomes 'ad' (abbreviation for advertisement).
'interrupts' means one lot of letters goes inside another.
'fight' becomes 'brawl' (brawl is a kind of fight).
'ad' placed within 'brawl' is 'BRADAWL'.
'it's' is the link.
(Other definitions for bradawl that I've seen before include "Boring tool" , "Piercing tool" , "it has a point" , "sharp-pointed object" , "Tool for making holes in wood" .)