Detective apprehending old group of scientists in south western area (6)
I believe the answer is:
dorset
'south western area' is the definition.
The definition suggests a singular noun which matches the answer.
'detective apprehending old group of scientists in' is the wordplay.
'detective' becomes 'det' (abbreviation for detective).
'apprehending' is an insertion indicator.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'group of scientists in' becomes 'rs' (I can't explain this - if you can you should believe this answer much more).
'o'+'rs'='ors'
'det' enclosing 'ors' is 'DORSET'.
Can you help me to learn more?
(Other definitions for dorset that I've seen before include "County adjoining 1" , "Sorted out the southern English county" , "Hardy country" , "South coast county" , "A SW county" .)