Lines inserted in successful work The Crown (7)
I believe the answer is:
hilltop
'crown' is the definition.
(I know that hilltop is a type of crown)
'lines inserted in successful work' is the wordplay.
'lines' becomes 'll' (an abbreviation for line written twice).
'inserted in' means one lot of letters goes inside another.
'successful' becomes 'hit' (I've seen this in another clue).
'work' becomes 'op' (common abbreviation for 'opus').
'll' placed into 'hit' is 'hillt'.
'hillt'+'op'='HILLTOP'
'the' acts as a link.
(Other definitions for hilltop that I've seen before include "Brow of mound" , "Crest or crown of an upland area" , "Summit" , "Prominent place" , "Peak of an incline" .)