Fuel supplied by dear character endlessly (6)
I believe the answer is:
petrol
'fuel' is the definition.
(petrol is a kind of fuel)
'dear character endlessly' is the wordplay.
'dear' becomes 'pet' (I've seen this in other clues).
'character' becomes 'role' (synonyms).
'endlessly' means to remove the last letter.
'role' with its last letter removed is 'rol'.
'pet'+'rol'='PETROL'
'supplied by' is the link.
(Other definitions for petrol that I've seen before include "Fuel for road vehicles" , "Liquid fuel" , "Common motor fuel" , "Gasoline" , "Common car fuel" .)