Organisation for education of children in developing countries (6)
I believe the answer is:
unicef
'organisation for education of children in developing countries' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for unicef that I've seen before include "UN organisation responsible for aid to children" , "International organisation for education of children in developing countries" , "Organisation for helping children and mothers in developing countries" , "international agency" , "UN children's organisation" .)