Establishment no-one has a pop at? (9)
I believe the answer is:
orphanage
'establishment' is the definition.
(I know that orphanage is a type of institution)
'no-one has a pop at?' is the wordplay.
I cannot really understand how this works, but
'no' could be 'o' (O resembles 0) and 'o' is present in the answer.
'one' could be 'an' (an apple is one apple) and 'an' is present in the answer.
'a' is within the answer.
This may be the basis of clue (or it may be nonsense).
(Other definitions for orphanage that I've seen before include "building" , "with deprived children" , "Home for parentless children" , "special home" , "left children here?" .)