Man's place is in his area, mostly unsettled (5,3)
I believe the answer is:
irish sea
'man's place' is the definition.
The definition suggests a singular noun which matches the answer.
'is in his area mostly unsettled' is the wordplay.
'in' means one lot of letters goes inside another.
'mostly' means to remove the last letter (most but not all of the word).
'unsettled' is an anagram indicator.
'his'+'area'='hisarea'
'hisarea' with its last letter taken off is 'hisare'.
'hisare' with letters rearranged gives 'irhsea'.
'is' going into 'irhsea' is 'IRISH SEA'.
Can you help me to learn more?
(Other definitions for irish sea that I've seen before include "Man's environment" , "Main" , "It separates Ireland from England and Wales" , "Waters around IOM" , "It lies between England and us" .)