Maybe a potato bin, I’m not sure (5)
I believe the answer is:
tuber
'maybe a potato' is the definition.
'bin i'm not sure' is the wordplay.
'bin' becomes 'tub'.
'i'm not sure' becomes 'er' (expression of hesitation).
'tub'+'er'='TUBER'
(Other definitions for tuber that I've seen before include "Fleshy underground part of a stem, often used as food" , "Fleshy underground root" , "Root eg of potato" , "Potato, for example" , "or still vegetating?" .)