In holy place I do His work (8)
I believe the answer is:
minister
'i do his work' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'in holy place' is the wordplay.
'in' means one lot of letters goes inside another.
'holy' becomes 'minter' (I can't explain this - if you can you should believe this answer much more).
'place' becomes 'is' (I've seen this in other clues).
'minter' going around 'is' is 'MINISTER'.
Can you help me to learn more?
(Other definitions for minister that I've seen before include "Senior politician" , "Holder of office in government or church" , "Form of address" , "Merit sin (anag.)" , "One of the clergy" .)