Former president securing one initially historic victory (7)
I believe the answer is:
triumph
'victory' is the definition.
(I know that triumph is a type of victory)
'former president securing one initially historic' is the wordplay.
'former president' becomes 'trump' (Donald Trump. I am not sure about the 'former' bit.).
'securing' is an insertion indicator.
'one' becomes 'i' (Roman numeral).
'initially' says to take the initial letters.
The initial letter of 'historic' is 'h'.
'trump' placed around 'i' is 'triump'.
'triump'+'h'='TRIUMPH'
Can you help me to learn more?
(Other definitions for triumph that I've seen before include "Successful ending of a struggle or contest" , "Victory - jubilation" , "Exultant victory" , "Great victory or achievement" , "hit" .)