Handle roughly 1000 gold lines initially (4)
I believe the answer is:
maul
'handle roughly' is the definition.
(I've seen this before)
'1000 gold lines initially' is the wordplay.
'm000' becomes 'm' ('m' can be a synonym of '1000'**).
'gold' becomes 'au' (Au is the chemical symbol for gold).
'initially' suggests taking the first letters.
The first letter of 'lines' is 'l'.
'm'+'au'+'l'='MAUL'
(Other definitions for maul that I've seen before include "Handle roughly; loose scrum" , "Maltreat roughly" , "Manhandle" , "Batter - lacerate" , "Injure seriously -- heavy hammer" .)