One surveying houses large roots affected (10)
I believe the answer is:
astrologer
'one surveying houses' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'large roots affected' is the wordplay.
'affected' is an anagram indicator.
'large'+'roots'='largeroots'
'largeroots' is an anagram of 'ASTROLOGER'.
Can you help me to learn more?
(Other definitions for astrologer that I've seen before include "Fortune-teller using zodiac" , "Compiler of star charts" , "One who reads the stars" , "Horoscopist" , "Studier of the supposed influence of stars" .)