Girl, violently ill, supported by youth leader (4)
I believe the answer is:
lily
'girl' is the definition.
(I've seen this before)
'violently ill supported by youth leader' is the wordplay.
'violently' indicates an anagram.
'supported by' says to put letters next to each other (letters go below - in down clue).
'youth leader' becomes 'y' (I've seen this in other clues).
'ill' anagrammed gives 'lil'.
'lil'+'y'='LILY'
(Other definitions for lily that I've seen before include "Trumpet-shaped flowering plant" , "Flower; girl's name" , "Fragrant bulbous plant" , "Plant with large trumpet-shaped flowers" , "Flowering bulb" .)