Casts lines after Thursday (6)
I believe the answer is:
throws
'casts' is the definition.
('throw' can be a synonym of 'cast')
'lines after thursday' is the wordplay.
'lines' becomes 'rows' (row is a kind of line).
'after' is a charade indicator (letters next to each other).
'thursday' becomes 'th' ('Th' can be a synonym of 'thursday').
'rows' put after 'th' is 'THROWS'.
(Other definitions for throws that I've seen before include "Chucks" , "Casts or hurls" , "Propels through the air" , "Hurls, flings" .)