Insignificant number getting married in a cathedral ultimately? (7)
I believe the answer is:
nominal
'insignificant' is the definition.
(as in a nominal fee)
'number getting married in a cathedral ultimately?' is the wordplay.
'number' becomes 'no' (abbreviation for 'number').
'getting' is a charade indicator (letters next to each other).
'married' becomes 'm' (abbreviation, e.g. in genealogy).
'ultimately?' indicates one should take the final letters (I've seen 'ultimately' mean this).
The final letter of 'cathedral' is 'l'.
'no'+'m'+'in'+'a'+'l'='NOMINAL'
(Other definitions for nominal that I've seen before include "Peppercorn rent" , "So called" , "In name only or token payment" , "Minor" , "In name or form only" .)