Passing MP here befuddled with ale (9)
I believe the answer is:
ephemeral
'passing' is the definition.
(synonyms)
'mp here befuddled with ale' is the wordplay.
'befuddled with' indicates anagramming the letters.
'mp'+'here'='mphere'
'mphere' mixed up with 'ale' can make 'EPHEMERAL'.
(Other definitions for ephemeral that I've seen before include "just for a day?" , "Short-lived, passing quickly" , "life's too short" , "A mere help (anag) - short-lived" , "staying for a little while" .)