A fabric that is woven as and when one pleases (2,4)
I believe the answer is:
at will
'is woven as and when one pleases' is the definition.
I can't judge whether this defines the answer.
'a fabric' is the wordplay.
'fabric' becomes 'twill' (type of fabric).
'a'+'twill'='AT WILL'
'that' acts as a link.
Can you help me to learn more?
(Other definitions for at will that I've seen before include "Freely" , "when one wants" , "According to one's own inclination" , "whenever you want" , "When I choose" .)