Part of church Liberal abandoned by mistake (4)
I believe the answer is:
apse
This might be a double definition.
'part' is the first definition.
(I have seen 'Part of church ' mean 'apse' so perhaps 'part' could also mean 'apse')
'church liberal abandoned by mistake' is the second definition.
'apse' can be an answer for 'church' (I've seen this before). I'm not certain of the 'liberal abandoned by mistake' bit.
'of' is the link.
(Other definitions for apse that I've seen before include "Domed section of a church" , "Strange peas in the church recess" , "Large recess in church" , "Part of a church with the altar" , "Peas (anag) -- part of a church" .)