Deny one is about to become a senior member (7)
I believe the answer is:
doyenne
'a senior member' is the definition.
(I've seen this in another clue)
'deny one is about' is the wordplay.
'is about' is an anagram indicator.
'deny'+'one'='denyone'
'denyone' anagrammed gives 'DOYENNE'.
'to become' is the link.
(Other definitions for doyenne that I've seen before include "highly-respected" , "An older academic" , "Senior lady in profession" , "Senior person" , "Respected lady" .)