Wife invested in African currency, an African (7)
I believe the answer is:
rwandan
'african' is the definition.
(Rwanda is an African country)
'wife invested in african currency an' is the wordplay.
'wife' becomes 'w' (abbreviation).
'invested in' is an insertion indicator.
'african currency' becomes 'rand' (currency of South Africa).
'w' placed within 'rand' is 'rwand'.
'rwand'+'an'='RWANDAN'
(Other definitions for rwandan that I've seen before include "Eg, a native of Kigali" , "African chap" , "Kigali native, perhaps" , "African native" , "From a central African country" .)