Picks pockets of two coppers (4)
I believe the answer is:
dips
'picks pockets' is the definition.
The answer and definition can be both shapes as well as being plural nouns.
Maybe you can see an association between them that I can't see?
'two coppers' is the wordplay.
'two coppers' can mean two substitutions for 'copper'.
'copper' becomes 'DI' (detective inspector, type of copper).
'copper' becomes 'ps' (I can't explain this - if you can you should believe this answer much more).
'di'+'ps'='DIPS'
'of' acts as a link.
Can you help me to learn more?
(Other definitions for dips that I've seen before include "Briefly immerses" , "Lowers into liquid" .)