Room to robe holy man in pretty clothing (6)
I believe the answer is:
vestry
'room' is the definition.
(I know that vestry is a type of room)
'robe holy man in pretty clothing' is the wordplay.
'robe' becomes 't' (I can't justify this - if you can you should give a lot more credence to this answer).
'holy man' becomes 's'.
'in' means one lot of letters goes inside another.
'pretty' becomes 'very' (pretty can mean very or considerably).
'clothing' indicates putting letters inside (some letters cover up or clothe others).
's' inserted inside 'very' is 'vesry'.
't' going within 'vesry' is 'VESTRY'.
'to' acts as a link.
Can you help me to learn more?
(Other definitions for vestry that I've seen before include "Parochial meeting-room in church" , "meeting of parishioners" , "Church sacristy" , "Small room attached to church" , "Church room where clergy dress themselves" .)