Declare a victory to old wife (4)
I believe the answer is:
avow
'declare' is the definition.
(I know that avow is a type of acknowledge)
'a victory to old wife' is the wordplay.
'victory' becomes 'v'.
'to old' becomes 'o' (common abbreviation eg in OE for Old English).
'wife' becomes 'w'.
'a'+'v'+'o'+'w'='AVOW'
(Other definitions for avow that I've seen before include "Assert/confess openly" , "acknowledge" , "Admit openly" , "Declare - affirm" , "Asseverate" .)