Work flat out at the laundry (4)
I believe the answer is:
iron
'work flat' is the definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Maybe you can see an association between them that I can't see?
'out at the laundry' is the wordplay.
'out' means one lot of letters goes inside another.
'at' becomes 'in' (synonymous in some cases - eg at school, in school).
'the laundry' becomes 'ro' (I can't explain this - if you can you should believe this answer much more).
'in' enclosing 'ro' is 'IRON'.
Can you help me to learn more?
(Other definitions for iron that I've seen before include "Ferrous metal" , "Smooth; element" , "Main element in steel" , "Revolver" , "uncompromising" .)