Visitor admits address is helpful for someone who wants to go for walks (8)
I believe the answer is:
calliper
'visitor admits address is helpful for someone who wants to go for walks' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how one could define the other.
'visitor admits address' is the wordplay.
'visitor' becomes 'caller' (caller is a kind of visitor).
'admits' means one lot of letters goes inside another.
'address' becomes 'ip' (I can't justify this - if you can you should believe this answer much more).
'caller' going around 'ip' is 'CALLIPER'.
Can you help me to learn more?
(Other definitions for calliper that I've seen before include "Instrument for measuring the distance between two points" , "Instrument to measure distance between two points" , "Measuring device with two hinged prongs attached to a scale" .)