Unusually diffident being involved with a sexier title for the Queen (5,11)

'title for the queen' is the definition.
(Latin for 'Defender of the Faith')

'unusually diffident being involved with a sexier' is the wordplay.
I cannot really see how this works, but
'being' could be 'ens' (I've seen this in other clues) and 'ens' is found in the answer.
'a' is found in the answer.
This explanation may well be incorrect...