Own up now Frenchman has sex appeal (5)
I believe the answer is:
admit
'own up' is the definition.
(I've seen this in another clue)
'now frenchman has sex appeal' is the wordplay.
'now' becomes 'AD' (AD, Anno Domini, as opposed to BC, Before Christ).
'frenchman' becomes 'M' (abbreviation for Monsieur - like 'Mr').
'has' is a charade indicator (letters next to each other).
'sex appeal' becomes 'it'.
'ad'+'m'+'it'='ADMIT'
(Other definitions for admit that I've seen before include "Confess - let in" , "Accept" , "Profess" , "Disclose" , "Confess (to something)" .)