Spoils a masterly piece of verse (4)
I believe the answer is:
mars
'spoils' is the definition.
('mar' can be a synonym of 'spoil')
'a masterly piece of verse' is the wordplay.
I cannot really see how this works, but
'a' is found in the answer.
'piece' could be 'r' (abbreviation for Rook) and 'r' is found in the answer.
The remaining letters 'ms' is a valid word which might be clued in a way I don't understand.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for mars that I've seen before include "Where Beagle 2 was landed on 25 December 2003" , "Injures - god of war" , "RS [RED STAR] (not technically)" , "Spoils - planet" , "blights" .)