Argument about curtailment of embroidery to finish church feature (4,6)
I believe the answer is:
rose window
'church feature' is the definition.
(I've seen this in another clue)
'argument about curtailment of embroidery to finish' is the wordplay.
'argument' becomes 'row' (to row is to argue).
'about' indicates putting letters inside.
'curtailment of' means to remove the last letter (to curtail is to cut short).
'embroidery' becomes 'sewing'.
'to finish' becomes 'do' ().
'sewing' with its last letter taken away is 'sewin'.
'sewin'+'do'='sewindo'
'row' going around 'sewindo' is 'ROSE-WINDOW'.
(Other definitions for rose window that I've seen before include "feature in church" , "Light" .)