Senior member having a desire to act (5)
I believe the answer is:
doyen
'senior member' is the definition.
(a senior or respected figure)
'a desire to act' is the wordplay.
'a desire' becomes 'yen' (yen can mean a longing or desire).
'to' means one lot of letters go next to another (I've seen this in other clues).
'act' becomes 'do' (to do is to act or execute a task).
'yen' put after 'do' is 'DOYEN'.
'having' is the link.
(Other definitions for doyen that I've seen before include "Man who is the senior in his profession" , "Dean of an academy" , "Greatly respected person" , "Senior man of a group" , "Senior member of a professional group" .)