One struggling to breathe because of the smoke? (6)
I believe the answer is:
gasper
'the smoke?' is the definition.
(slang term for a cigarette)
'one struggling to breathe' is the wordplay.
'one struggling' becomes 'er' (I am not sure about this - if you are sure you should believe this answer much more).
'to' is a charade indicator (letters next to each other) (I've seen this in other clues).
'breathe' becomes 'gasp' (gasping is a kind of breathing).
'er' put after 'gasp' is 'GASPER'.
'because of' acts as a link.
Can you help me to learn more?
(Other definitions for gasper that I've seen before include "who can hardly get the words out?" , "Ciggie" , "One puffing" , "Pagers (anag) - cigarette (slang)" , "Grapes (anag) -- cigarette (slang)" .)