Say again about fuel (6)
I believe the answer is:
repeat
'say again' is the definition.
(I've seen this in another clue)
'about fuel' is the wordplay.
'about' becomes 're' (regarding).
'fuel' becomes 'peat' (peat is a kind of fuel).
're'+'peat'='REPEAT'
(Other definitions for repeat that I've seen before include "Go over" , "Divulge" , "Reiterate" , "Say again, or burp" , "Say, do or occur again" .)