Observe church shelter spoilt child inside (9)
I believe the answer is:
celebrate
'observe' is the definition.
(I know that celebrate is a more specific form of observe)
'church shelter spoilt child inside' is the wordplay.
'church' becomes 'CE' (abbreviation for Church of England).
'shelter' becomes 'lee' (as in lee side, the side sheltered from wind).
'spoilt child' becomes 'brat' (I've seen this before).
'inside' is an insertion indicator.
'lee' enclosing 'brat' is 'lebrate'.
'ce'+'lebrate'='CELEBRATE'
(Other definitions for celebrate that I've seen before include "Publicly praise (someone)" , "Honour or commemorate" , "Rejoice or commemorate" , "Be festive" , "Have a party to mark a happy event" .)