Curse of drivers inhaling endless methane supply (8)
I believe the answer is:
anathema
'curse' is the definition.
(anathema is a kind of curse)
'drivers inhaling endless methane supply' is the wordplay.
'drivers' becomes 'aa' (I've seen this in other clues).
'inhaling' is an insertion indicator.
'endless' means to remove the last letter.
'supply' indicates anagramming the letters (supply of letters to make).
'methane' with its last letter removed is 'methan'.
'methan' anagrammed gives 'nathem'.
'aa' going around 'nathem' is 'ANATHEMA'.
'of' is the link.
(Other definitions for anathema that I've seen before include "Formal curse leading to excommunication" , "person cannot stand" , "Something hated" , "denunciation" , "detestable" .)