Vegetable giving brother, 100, endless abdominal pain (8)
I believe the answer is:
broccoli
'vegetable' is the definition.
(I know that Broccoli is a type of vegetable)
'brother 100 endless abdominal pain' is the wordplay.
'brother' becomes 'bro' (short for brother).
'100' becomes 'C' (Roman numeral).
'endless' means to remove the last letter.
'abdominal pain' becomes 'colic' (I've seen this before).
'colic' with its final letter taken away is 'coli'.
'bro'+'c'+'coli'='BROCCOLI'
'giving' is the link.
(Other definitions for broccoli that I've seen before include "Green/purplish vegetable" , "Vegetable in a strange cool crib" , "producer in pictures?" , "Calabrese" , "Food" .)