Curiously evenly folded clays (5)
I believe the answer is:
oddly
'curiously' is the definition.
('oddly' can be a synonym of 'curiously')
'evenly folded clays' is the wordplay.
'evenly' means one should take alternating letters (even-numbered letters only).
'folded'+'clays'='foldedclays'
The alternate letters of 'foldedclays' are 'ODDLY'.
(Other definitions for oddly that I've seen before include "not in the usual way" , "Unusually" , "Strangely, curiously" , "in a curious way" , "Weirdly" .)