Interwoven material mine that captivates the French (5)
I believe the answer is:
Here is my best explanation:
'interwoven material' is the definition.
Although both the answer and definition are singular nouns, I don't understand how one could define the other.
'mine that captivates the french' is the wordplay.
'mine' becomes 'pit' (down the pit).
'that captivates' indicates putting letters inside.
'the french' becomes 'la'.
'pit' placed around 'la' is 'PLAIT'.
(Other definitions for plait that I've seen before include "A rope of hair (5)", "Braided tress", "Braided pigtail", "A twine of hair", "Stranded length of hair", "Length of woven hair", "Braided hair", "Stranded piece of hair", "Weave; queue" and "Intertwine".)