One smoker, awfully tedious (7)
I believe the answer is:
irksome
'tedious' is the definition.
(I've seen this before)
'one smoker awfully' is the wordplay.
'one' becomes 'i' (Roman numeral).
'awfully' indicates anagramming the letters.
'smoker' anagrammed gives 'rksome'.
'i'+'rksome'='IRKSOME'
(Other definitions for irksome that I've seen before include "'Tedious, tiresome (7)'" , "Tiresome, irritating" , "Troublesome, vexing" , "'Annoying, irritating or boring (7)'" , "bugging" .)