Religious man that is in pub is a hindrance (7)
I believe the answer is:
barrier
'hindrance' is the definition.
(barrier is a kind of hindrance)
'religious man that is in pub' is the wordplay.
'religious man' becomes 'rr' (I can't justify this - if you can you should believe this answer much more).
'that is' becomes 'ie' (short for Latin 'id est', 'that is').
'in' means one lot of letters goes inside another.
'pub' becomes 'bar' (both are drinking establishments).
'rr'+'ie'='rrie'
'rrie' put into 'bar' is 'BARRIER'.
'is a' acts as a link.
Can you help me to learn more?
(Other definitions for barrier that I've seen before include "Impediment" , "Rear rib may present obstacle" , "It impedes free movement" , "Obstacle to movement" , "Obstacle to progress" .)