Mormon wandering in valley briefly finds place of rest (6,4)
I believe the answer is:
common room
'place of rest' is the definition.
'mormon wandering in valley briefly' is the wordplay.
'wandering' is an anagram indicator.
'in' is an insertion indicator.
'valley' becomes 'coomb' (I've seen this before).
'briefly' means to remove the last letter.
'mormon' with letters rearranged gives 'ommonr'.
'coomb' with its final letter taken off is 'coom'.
'ommonr' placed within 'coom' is 'COMMON-ROOM'.
'finds' is the link.
(Other definitions for common room that I've seen before include "for the rest of the teachers" , "Helpful deed" .)