Throat condition (5)
'throat condition' is the definition.
(throat inflammation affecting children)
This is the entire clue.
(Other definitions for croup that I've seen before include "Children's disease causing difficulty in breathing" , "Throat infection; horse's hindquarters" , "Complaint of small children" , "Throat condition with a hacking cough" , "Hard cough and difficult breathing in children" .)
'throat condition' is the definition.
(I've seen this in another clue)
This is all the clue.
(Another definition for strep that I've seen is " bacterium".)