Coppers may get old, yet still be progressive (4)
I believe the answer is:
plod
'coppers may get old yet still be progressive' is the definition.
I can't tell whether this defines the answer.
'coppers may get old' is the wordplay.
I cannot really see how this works, but
'coppers' could be 'p' and 'p' is located in the answer.
an anagram of 'old' is 'lod' which is within the answer.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for plod that I've seen before include "Slow heavy walk" , "Walk slowly and laboriously" , "Walk with effort" , "Policeman - walk slowly" , "Walk slowly and heavily" .)