What barker calls smoke (4,2)
I believe the answer is:
roll up
I believe this is a double definition.
'what barker calls' is the first definition.
(a barker or tout might shout 'roll up! roll up!')
'smoke' is the second definition.
(as in rolling a cigarette)
(Other definitions for roll up that I've seen before include "Fairground barker's exhortation" , "smoke" , "Appear" , "Invitation to come" , "Arrive -- handmade cigarette (4,2;4-2)" .)