Terribly ill Yankee gets flower (4)
I believe the answer is:
lily
'flower' is the definition.
(I've seen this before)
'terribly ill yankee' is the wordplay.
'terribly' indicates anagramming the letters.
'yankee' becomes 'y' (phonetic alphabet: alpha, bravo, charlie etc.).
'ill' with letters rearranged gives 'lil'.
'lil'+'y'='LILY'
'gets' acts as a link.
(Other definitions for lily that I've seen before include "Flower -- girl" , "Bulbous plant with trumpet-shaped flowers" , "Bulb with showy, typically pendulous flowers" , "Flower of purity" , "- - Allen, singer" .)