Copper with black coat and cloak placed inside skip (3,1,5)
I believe the answer is:
cut a caper
'skip' is the definition.
(I've seen this before)
'copper with black coat and cloak placed inside' is the wordplay.
'copper with' becomes 'cu' (chemical symbol. I am not sure about the 'with' bit.).
'black coat' becomes 'tar' (I've seen this before).
'and' means one lot of letters go next to another.
'cloak' becomes 'cape' (cape is a kind of cloak).
'placed inside' means one lot of letters goes inside another.
'cu'+'tar'='cutar'
'cutar' placed around 'cape' is 'CUT A CAPER'.
(Other definitions for cut a caper that I've seen before include "Make a playful skipping movement" , "When making tartar sauce, one has to" , "Bound" , "Skip or jump playfully" , "to make a start on tartare sauce" .)