A roll and crackers on time in great supply (8)
I believe the answer is:
abundant
'a roll and crackers on time in great supply' is the definition.
I can't judge whether this defines the answer.
'a roll and crackers on time' is the wordplay.
'roll' becomes 'bun' (synonyms).
'crackers' indicates anagramming the letters (informal term for mad).
'on' is a charade indicator (letters next to each other).
'time' becomes 't' (abbreviation).
'and' with letters rearranged gives 'dan'.
'a'+'bun'+'dan'+'t'='ABUNDANT'
Can you help me to learn more?
(Other definitions for abundant that I've seen before include "Guardian spirit" , "Existing in large quantities, plentiful" , "full" , "Exuberant" , "Present in great quantity" .)