Main part of perpendicular churches (4)
I believe the answer is:
arch
'main' is the definition.
(I've seen this before)
'part of perpendicular churches' is the wordplay.
'part of' indicates a hidden word.
'ARCH' is hidden in the letters of 'perpendicular churches'.
(Other definitions for arch that I've seen before include "Chief; bow" , "one under a foot?" , "Consummate" , "one that may have fallen" , "Clever" .)