It is used to see a sound place to build (5)
I believe the answer is:
sight
'it is used to' is the definition.
The definition suggests a singular noun which matches the answer.
'a sound place to build' is the wordplay.
'a sound' shows a homophone (sound like).
'place to build' becomes 'site' (I've seen this in another clue).
'site' sounds like 'SIGHT'.
'see' acts as a link.
Can you help me to learn more?
(Other definitions for sight that I've seen before include "Sense" , "Visual perception" , "Show" , "a great deal" , "A great many" .)