Never run out of puff? (5-5)
I believe the answer is:
chain-smoke
'puff?' is the definition.
(thesaurus)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for chain-smoke that I've seen before include "Get through fags one after the other" , "Get through cigarettes one after another" , "Light one fag after another" , "Keep dragging" , "Puff non-stop" .)