Language of love in southern African country (6)
I believe the answer is:
somali
'language' is the definition.
(I know that Somali is a modern language)
'love in southern african country' is the wordplay.
'love' becomes 'o' (love means zero in tennis).
'in' indicates putting letters inside.
'southern' becomes 's' (abbreviation).
'african country' becomes 'mali' (country in Africa).
's'+'mali'='smali'
'o' put within 'smali' is 'SOMALI'.
'of' acts as a link.
(Other definitions for somali that I've seen before include "East African national" , "African language" , "native language" , "From a part of northeast Africa" , "1 [GCSE]" .)