God, for one Rector, will involve source of tension (5)
I believe the answer is:
satyr
'god' is the definition.
(satyr is a kind of god)
'for one rector will involve source of tension' is the wordplay.
'for one' becomes 'say' (both can mean 'for example').
'rector will' becomes 'r' (I can't explain this - if you can you should give a lot more credence to this answer).
'involve' means one lot of letters goes inside another.
'source of' indicates taking the first letters.
The first letter of 'tension' is 't'.
'say'+'r'='sayr'
'sayr' placed around 't' is 'SATYR'.
Can you help me to learn more?
(Other definitions for satyr that I've seen before include "Lustful, drunken woodland god" , "Woodland spirit" , "Greek sylvan deity" , "Classical deity" , "Woodland god - sexual predator" .)