Church vestment: a pound (3)
I believe the answer is:
alb
'church vestment' is the definition.
(I've seen this before)
'a pound' is the wordplay.
'pound' becomes 'lb' ('lb' can be a synonym of 'pound').
'a'+'lb'='ALB'
(Other definitions for alb that I've seen before include "clerical belongings" , "Without hindrance" , "Clerical vestment." , "Priests robe made in Balbriggan" , "Devotional vestment" .)