Wasting sovereign and coppers on serving man wearing Spanish outfit (9)
I believe the answer is:
regicidal
'wasting sovereign' is the definition.
The definition suggests an adjective which matches the answer.
'coppers on serving man wearing spanish outfit' is the wordplay.
I cannot really understand how this works, but
'on' could be 're' ('on' can be mean 'with reference to') and 're' is located in the answer.
'man' could be 'dal' and 'dal' is found in the answer.
This may be the basis of the clue (or it may be nonsense).
'and' is the link.
Can you help me to learn more?
(Other definitions for regicidal that I've seen before include "taking out ruler?" , "top-level murder" , "like Macbeth?" .)