Picture opportunity for children to have a day off school (5)
I believe the answer is:
inset
I believe this is a double definition.
'picture' is the first definition.
(inset is a kind of picture)
'opportunity for children to have a day off school' is the second definition.
(as in an inset day at a school)
(Other definitions for inset that I've seen before include "Place within" , "Picture inside a larger one" , "Training during term time for teachers in state schools" , "Not taking proper care" , "lesser feature" .)