Reveal Frenchman's one request after getting married (6)
I believe the answer is:
unmask
'reveal' is the definition.
(I've seen this before)
'frenchman's one request after getting married' is the wordplay.
'frenchman's one' becomes 'un' (one in French).
'request' becomes 'ask' ('ask' can be a synonym of 'request').
'after' is a charade indicator (letters next to each other).
'getting married' becomes 'm' (I've seen this in other clues).
'ask' after 'm' is 'mask'.
'un'+'mask'='UNMASK'
(Other definitions for unmask that I've seen before include "Expose, strip away concealment" , "Disclose (the hidden nature of)" , "Expose, remove face covering" , "Expose, remove cover" , "Expose and denounce" .)