Bitterness constrains good cobblers (5)
I believe the answer is:
'bitterness constrains good cobblers' is the definition.
I can't tell whether this defines the answer.
'bitterness constrains good' is the wordplay.
'bitterness' becomes 'bile' (I've seen this in other clues).
'constrains' is an insertion indicator.
'good' becomes 'g' (abbreviation).
'bile' going around 'g' is 'BILGE'.
Can you help me to learn more?
(Other definitions for bilge that I've seen before include "bull" , "Dirty water collecting on a vessel" , "Piffle - part of hull" , "Lower part of hull; nonsense" , "Nonsense (informal)" .)