A duty to convert with Mass in part of temple (6)
I believe the answer is:
adytum
'part of temple' is the definition.
The definition suggests a singular noun which matches the answer.
'a duty to convert with mass' is the wordplay.
'to convert with' indicates anagramming the letters (I've seen 'converted' mean this).
'mass' becomes 'm' (symbol used in Physics e.g. f=ma).
'duty' anagrammed with 'm' can make 'dytum'.
'a'+'dytum'='ADYTUM'
'in' acts as a link.
Can you help me to learn more?
(Other definitions for adytum that I've seen before include "sacred space" , "inner sanctum" , "Temple sanctuary" , "Inner room" , "ancient sanctuary" .)