Keep copyright with least trouble (6)
I believe the answer is:
castle
'keep' is the definition.
(I've seen this before)
'copyright with least trouble' is the wordplay.
'copyright' becomes 'c' (as in the copyright symbol, a C in a circle).
'with' means one lot of letters go next to another.
'trouble' is an anagram indicator.
'least' anagrammed gives 'astle'.
'c'+'astle'='CASTLE'
(Other definitions for castle that I've seen before include "ancient building?" , "a piece in the corner" , "Chess piece and grand house" , "making a move" , "Man on board" .)