Health hazard in the Commons? Run for it! (8)
I believe the answer is:
housefly
'health hazard' is the definition.
(fly which often contaminates food)
'the commons? run for it' is the wordplay.
'the commons?' becomes 'house' (House of Commons).
'run for it' becomes 'fly' (both can mean to run away).
'house'+'fly'='HOUSEFLY'
'in' acts as a link.
(Other definitions for housefly that I've seen before include "Common winged insect" , "That which is swatted in the home" , "Domestic insect" , "pest" .)