Warm beverage that you initially infused with rum (5)
I believe the answer is:
toddy
'warm beverage' is the definition.
'toddy' can be an answer for 'beverage' (I have seen 'Alcoholic beverage ' mean 'toddy' so perhaps 'beverage' could also mean 'toddy'). I am not sure about the 'warm' bit.
'that you initially infused with rum' is the wordplay.
'initially' suggests taking the first letters.
'infused with' means one lot of letters goes inside another.
'rum' becomes 'odd' (rum can mean strange or dubious).
The initial letters of 'that you' is 'ty'.
'ty' going around 'odd' is 'TODDY'.
Can you help me to learn more?
(Other definitions for toddy that I've seen before include "A hot tipple" , "Sap of wine-palm, as a drink" , "Spirits with hot water, sugar and spices" , "Mixture of spirits, sugar and hot water" , "Hot spirituous drink" .)