24ac Copper market failed 3,3 C?T ?U?
26ac Stone work filling in wall (4)O?A?
27ac Cosiest area to catch some sleep (6) S?E???
28ac Is in heat that's ominous (8) S?N?S?E?
23dn Clumsy writer about to get into it (5) I?E??
Many thanks to all I think that's it but who knows
24a Cut Out copper= Cu+Tout
26a Opal work=op + (w)al(l)
27a Siesta in clue coSIEST Area
28a Sinister Sinter def. coalesce into a solid or porous mass by means of heating Sin(is)ter.
23d Inept pen about in it I(nep)t