Your sixth cherry rum beverage ends in poem (5)
I believe the answer is:
rhyme
'in poem' is the definition.
(I know that poem is a is part of of rhyme)
'your sixth cherry rum beverage ends' is the wordplay.
'ends' suggests the final letters.
The last letters of 'your sixth cherry rum beverage' are 'RHYME'.
(Other definitions for rhyme that I've seen before include "Charlie Farley for example?" , "anticipated by a nursery perhaps" , "(Of words) sound the same" , "Word for bird" , "Bit of poetry" .)