Drink containing rum, extremely tasty (5)
I believe the answer is:
toddy
'drink' is the definition.
(toddy is a type of drink)
'containing rum extremely tasty' is the wordplay.
'containing' indicates putting letters inside.
'rum' becomes 'odd' (rum can mean strange or dubious).
'extremely' says to hollow out the word (remove centre letters) (only the extremes of the word are used).
'tasty' with its middle taken out is 'ty'.
'odd' placed inside 'ty' is 'TODDY'.
(Other definitions for toddy that I've seen before include "Sap of wine-palm, as a drink" , "Hot mixed drink" , "Hot spirituous drink" , "Hot drink of spirits with sugar and spices" , "Hot drink of alcohol" .)