Senior member aching after party (5)
I believe the answer is:
doyen
'senior member' is the definition.
(a senior or respected figure)
'aching after party' is the wordplay.
'aching' becomes 'yen' (I've seen this in another clue).
'after' means one lot of letters go next to another.
'party' becomes 'do' (do can informally mean a party).
'yen' put after 'do' is 'DOYEN'.
(Other definitions for doyen that I've seen before include "Greatly respected person" , "Senior member of a professional group" , "Dean of an academy" , "Senior member of a profession or academy" , "Senior male figure in a profession" .)