Standard type of telephone around South (10)
I believe the answer is:
touchstone
'standard' is the definition.
(synonyms)
'type of telephone around south' is the wordplay.
'type of telephone' becomes 'touchtone' (phone with buttons rather than a rotary dial).
'around' indicates putting letters inside.
'south' becomes 's' (synonyms).
'touchtone' placed around 's' is 'TOUCHSTONE'.
(Other definitions for touchstone that I've seen before include "Character in As You Like It" , "Jasper" , "stage clown" , "forest-dweller" , "Standard" .)