Language's current rules about welcoming greeting (7)
I believe the answer is:
swahili
'language's' is the definition.
(Swahili is an example)
'current rules about welcoming greeting' is the wordplay.
'current' becomes 'i' (symbol for electric current).
'rules' becomes 'laws' (law is a kind of rule**).
'about' says the letters should be written backwards.
'welcoming' is an insertion indicator (in sense of 'inviting in').
'greeting' becomes 'hi' (hi is a kind of greeting).
'i'+'laws'='ilaws'
'ilaws' in reverse letter order is 'swali'.
'swali' placed around 'hi' is 'SWAHILI'.
(Other definitions for swahili that I've seen before include "African tongue" , "Common language of E. Africa" , "African people" , "Common language in East Africa" , "E. African language" .)