Gallon consumed by renowned pilot Harry (6)
I believe the answer is:
badger
'harry' is the definition.
(both can mean to bother or harass)
'gallon consumed by renowned pilot' is the wordplay.
'gallon' becomes 'g' (abbreviation for the unit of liquid).
'consumed by' indicates putting letters inside.
'renowned pilot' becomes 'bader' (Second World War RAF pilot Douglas Bader).
'g' placed inside 'bader' is 'BADGER'.
(Other definitions for badger that I've seen before include "Nocturnal black and white animal" , "Harass - brock" , "quarry, perhaps" , "ride" , "Black and white burrower" .)