An insular, saintly female (6)
I believe the answer is:
helena
'saintly female' is the definition.
Although both the answer and definition are singular nouns, I cannot see how one could define the other.
'an insular' is the wordplay.
I cannot quite see how this works, but
'an' could be 'a' and 'a' is present in the answer.
The remaining letters 'helen' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for helena that I've seen before include "dreamy girl" , "- - Bonham-Carter, actress" , "Hermia's friend, rival (MND)" , "Could be Rubinstein" , "St ---, where Napoleon died" .)