Closing bars best at Henley, perhaps, when whiskey’s run out (5)
I believe the answer is:
outro
'closing bars' is the definition.
(closing bars of a piece of music)
'best at henley perhaps when whiskey's run out' is the wordplay.
I cannot really see how this works, but
'run' could be 'r' (cricket abbreviation) and 'r' is present in the answer.
an anagram of 'out' is 'uto' which is located in the left over letters.
A single letter 'o' remains which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
(Other definitions for outro that I've seen before include "bars closing" , "Piece ending programme" , "last lot of notes" , "Part that closes" .)