Vegetable giving brother terrible colic (8)
I believe the answer is:
Here is my best explanation:
'vegetable' is the definition.
(broccoli is a kind of vegetable)
'giving brother terrible colic' is the subsidiary indication.
'giving' says to put letters next to each other.
'brother' becomes 'bro'.
'terrible' indicates an anagram.
'colic' is an anagram of 'ccoli'.
'bro' next to 'ccoli' is 'broccoli'.
(Other definitions for broccoli that I've seen before include "Type of vegetable", "Sort of green cauli", "Green vegetable - producer of Bond films", "A variety of brassica", "Food", "A variety of cabbage", "Vegetable of cabbage family", "A hardy variety of cauliflower", "Vegetable in a strange cool crib" and "Vegetable whose Italian name means 'sprouts'".)