Clothe in undergarment the French discarded (4)
I believe the answer is:
gird
'clothe' is the definition.
Although both the answer and definition are verbs in their base form, I can't see how they can define each other.
'undergarment the french discarded' is the wordplay.
'undergarment' becomes 'girdle' (girdle is a kind of undergarment).
'the french' becomes 'le'.
'discarded' is a deletion indicator.
'girdle' with 'le' removed is 'GIRD'.
'in' acts as a link.
Can you help me to learn more?
(Other definitions for gird that I've seen before include "Encircle - fasten with belt" , "Surround" , "Put a belt on" , "ring" , "Steel" .)