Give conclusion to old wife (5)
I believe the answer is:
endow
'give' is the definition.
(endow can mean to give or bestow)
'conclusion to old wife' is the wordplay.
'conclusion' becomes 'end' (something's conclusion is its end).
'to old' becomes 'o' (common abbreviation eg in OE for Old English).
'wife' becomes 'w' (abbreviation).
'end'+'o'+'w'='ENDOW'
(Other definitions for endow that I've seen before include "Set up with money" , "Provide capital to ensure an income for an institution" , "Give money to" , "Provide as a gift" , "Give permanent income to" .)