Some heap seen in church recess? (4)
I believe the answer is:
apse
'church recess?' is the definition.
(part of a church)
'some heap seen in' is the wordplay.
'in' indicates a hidden word.
'APSE' is hidden in the letters of 'some heap seen'.
(Other definitions for apse that I've seen before include "inside church?" , "Recess at east end of church" , "Strange peas in the church recess" , "Part of a church with the altar" , "may be seen in church!" .)