Finish best at regatta, perhaps, or almost (5)
I believe the answer is:
outro
'almost' is the definition.
I know nothing about this answer so I cannot tell whether it can be defined by this definition.
'finish best at regatta perhaps or' is the wordplay.
'finish' says to take the final letters.
'at' is a charade indicator (letters next to each other) (I've seen this in other clues).
'regatta' becomes 'ou' (I can't explain this - if you can you should believe this answer much more).
'perhaps' indicates anagramming the letters.
The final letter of 'best' is 't'.
'or' with letters rearranged gives 'ro'.
't' after 'ou' is 'out'.
'out'+'ro'='OUTRO'
Can you help me to learn more?
(Other definitions for outro that I've seen before include "last lot of notes" , "bars closing" , "Part that closes" , "Piece ending programme" .)