Amelia is one admitting love affair (7)
I believe the answer is:
liaison
'love affair' is the definition.
(I've seen this before)
'amelia is one admitting' is the wordplay.
'admitting' indicates the answer is hidden within the clue (I've seen 'admits' mean this).
'LIAISON' is hidden within 'amelia is one'.
(Other definitions for liaison that I've seen before include "Co-operation; love affair" , "A contact or affair" , "Secretive affair" , "Connection - relationship" , "Channel of communication" .)