It lends inflexibility to a leader at church (6)
I believe the answer is:
starch
'it lends inflexibility' is the definition.
The definition suggests a singular noun which matches the answer.
'a leader at church' is the wordplay.
'a leader at' becomes 'star' (I can't justify this - if you can you should believe this answer much more).
'church' becomes 'ch' (common abbreviation).
'star'+'ch'='STARCH'
'to' is the link.
Can you help me to learn more?
(Other definitions for starch that I've seen before include "foodstuff" , "Stiffness of manner" , "Stiffening agent" , "Carbohydrate; stiffen" , "Formal quality" .)