Stunned response around high ground reduced for some time (6)
I believe the answer is:
awhile
'some time' is the definition.
(I have seen 'short time' mean 'awhile' so perhaps 'time' could also mean 'awhile')
'stunned response around high ground reduced' is the wordplay.
'stunned response' becomes 'awe'.
'around' is an insertion indicator.
'high ground' becomes 'hill' (I've seen this before).
'reduced' means to remove the last letter.
'hill' with its final letter taken away is 'hil'.
'awe' enclosing 'hil' is 'AWHILE'.
'for' acts as a link.
(Other definitions for awhile that I've seen before include "For a short time" , "briefly" , "a brief period" .)