Disco always has fuel (4)

I believe the answer is:

coal

'fuel' is the definition.
(coal is a kind of fuel)

'disco always has' is the wordplay.
'has' indicates the answer is hidden within the clue.
'COAL' is hidden within 'disco always'.

(Other definitions for coal that I've seen before include "Char" , "Solid fuel" , "Fossil fuel" , "Three domestic fuels" , "This consists mainly of carbon" .)

I've seen this clue in The Mirror.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.