Fish from bistro, a chub (5)
I believe the answer is:
roach
'fish' is the definition.
(roach is a kind of fish)
'from bistro a chub' is the wordplay.
'from' indicates the answer is hidden within the clue.
'ROACH' can be found hidden inside 'bistro a chub'.
(Other definitions for roach that I've seen before include "Something fishy here" , "Animal found in the water" , "member of family carp" , "Trim" , "Fish of the carp family" .)