Republic once putting an extra bar on fuel? (4)
I believe the answer is:
eire
'republic' is the definition.
(Irish name for Ireland)
'putting an extra bar on fuel?' is the wordplay.
I cannot quite understand how this works, but
'an' could be 'i' (Roman numeral for one) and 'i' is found within the answer.
'on' could be 're' (regarding) and 're' is located in the answer.
A single letter 'e' remains which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
'once' is the link.
(Other definitions for eire that I've seen before include "Republic across the water" , "Breakaway state" , "Official name of the Irish Republic, 1937-49" , "island" , "Northwest European country" .)